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Jim Thompson
Guest
Guest
Fri Feb 12, 2010 11:21 pm
On Fri, 12 Feb 2010 16:07:52 -0600, krw <krw_at_att.bizzzzzzzzzzz> wrote:
Quote:
On Fri, 12 Feb 2010 08:24:24 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 12 Feb 2010 10:03:11 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:
Build a man a fire, you keep him warm for a night. Set a man afire, you
keep him warm for the rest of his life. ;)
Cheers
Phil Hobbs
Got snow?
We have about 1" now. They cancelled work for today about 9:30 last
night. Since there was no snow this morning (it started about
10:00AM) I went into work. I was the only one there. My wife's
employer closed about 2:00, with less than 1" on the ground. The
streets are just now starting to get some slush on them. I guess it's
a good thing the locals are scared shitless of snow.
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 12 Feb 2010 10:03:11 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:
Build a man a fire, you keep him warm for a night. Set a man afire, you
keep him warm for the rest of his life. ;)
Cheers
Phil Hobbs
Got snow?
We have about 1" now. They cancelled work for today about 9:30 last
night. Since there was no snow this morning (it started about
10:00AM) I went into work. I was the only one there. My wife's
employer closed about 2:00, with less than 1" on the ground. The
streets are just now starting to get some slush on them. I guess it's
a good thing the locals are scared shitless of snow.
I can see the Superstition Mountains from here (they're about 60 miles
east of me), no snow even on top of them.
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
George Herold
Guest
Guest
Fri Feb 12, 2010 11:29 pm
On Feb 12, 11:23 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Fri, 12 Feb 2010 10:23:24 -0500, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
On 2/12/2010 9:52 AM, Jim Thompson wrote:
On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
On 2/11/2010 10:35 PM, George Herold wrote:
On Feb 11, 1:14 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams"
tmoran...@charter.net> wrote:
"Jim Thompson"<To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote in
messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd_at_4ax.com...
And a 2.5V "dead-band", but it _is_ precisely known, and temperature
stable. Interesting thought if you have high enough power supplies.
Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier.
Too bad they're so slow (hardly capable for audio). Does anyone make "fast"
regulators (without being stupid LDOs)?
Tim
If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?
Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.
I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.
John
Cool! I think I got it... though if I try it in the future and let
the smoke out of something... then I might have questions.
George H.
IIRC the LM395 is basically an LM309 with the voltage reference removed.
Emitter-follower regulators are nearly bulletproof unless you
discharge a cap into the output.
Cheers
Phil Hobbs
Close, but no cigar, LM395 = LM317 with some metal rearrangements.
I was thinking 317 but then I decided that the 395 was older than that.
I guess not.
I did this analysis for ICE back in 1980:
http://analog-innovations.com/SED/ICE-LM195-LM117.pdf
Additionally: Amusing myself with the thoughts of complementary-
follower-style power amplifiers made from LM317/LM337 pairs, it fails
because both, internally, are NPN's pass devices, so the LM337 has GBW
and stability issues plus it needs substantial idle load to stay
_vaguely_ stable.
Non-LDO three-terminal regulators are so trouble-free that it's easy to
confuse them with Newton's laws. ;)
Cheers
Phil Hobbs
LM1117 is an "MDO" regulator. It has an NPN pass transistor but a bit
lower dropout voltage than an LM317. Its ideal as a 3.3-to-1.25 volt
FPGA core voltage source... no resistors! My purchasing notes say "Do
not buy Fairchild per JL" but I can't recall why.
As with all vregs, one has to be careful about the output capacitors.
John- Hide quoted text -
- Show quoted text -
pcdhSpamMeSensel...@electrooptical.net> wrote:
On 2/12/2010 9:52 AM, Jim Thompson wrote:
On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
On 2/11/2010 10:35 PM, George Herold wrote:
On Feb 11, 1:14 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams"
tmoran...@charter.net> wrote:
"Jim Thompson"<To-Email-Use-The-Envelope-I...@My-Web-Site.com> wrote in
messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd_at_4ax.com...
And a 2.5V "dead-band", but it _is_ precisely known, and temperature
stable. Interesting thought if you have high enough power supplies.
Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier.
Too bad they're so slow (hardly capable for audio). Does anyone make "fast"
regulators (without being stupid LDOs)?
Tim
If you drive both adjust pins with the signal input, the 317 output is
Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output
through a couple of resistors, valued to set the idle current. Where's
the deadband?
Or you can take the output from the 317 output pin, with the 337 now
acting like a constant-current sink to the 317.
I like to use LM1117s as power emitter followers, inside the loop of
an opamp. That makes a cheap, well protected power driver, for load
cell excitation and such. I did a bunch of tests to see whether
flailing the adj pin can damage the regulator, and never managed to
break one.
John
Cool! I think I got it... though if I try it in the future and let
the smoke out of something... then I might have questions.
George H.
IIRC the LM395 is basically an LM309 with the voltage reference removed.
Emitter-follower regulators are nearly bulletproof unless you
discharge a cap into the output.
Cheers
Phil Hobbs
Close, but no cigar, LM395 = LM317 with some metal rearrangements.
I was thinking 317 but then I decided that the 395 was older than that.
I guess not.
I did this analysis for ICE back in 1980:
http://analog-innovations.com/SED/ICE-LM195-LM117.pdf
Additionally: Amusing myself with the thoughts of complementary-
follower-style power amplifiers made from LM317/LM337 pairs, it fails
because both, internally, are NPN's pass devices, so the LM337 has GBW
and stability issues plus it needs substantial idle load to stay
_vaguely_ stable.
Non-LDO three-terminal regulators are so trouble-free that it's easy to
confuse them with Newton's laws. ;)
Cheers
Phil Hobbs
LM1117 is an "MDO" regulator. It has an NPN pass transistor but a bit
lower dropout voltage than an LM317. Its ideal as a 3.3-to-1.25 volt
FPGA core voltage source... no resistors! My purchasing notes say "Do
not buy Fairchild per JL" but I can't recall why.
As with all vregs, one has to be careful about the output capacitors.
John- Hide quoted text -
- Show quoted text -
John L wrote:
My purchasing notes say "Do not buy Fairchild per JL" but I can't
recall why.
That's too bad I've always used the Fairchild parts. Only issue we
ever had was with cheap Jameco 'crap'.
George h.
Jon Kirwan
Guest
Guest
Sat Feb 13, 2010 1:59 am
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com>
wrote:
Quote:
This is an example of a common emitter voltage amplifier. It might be one of
the easiest stages to design. Normaly, I would start off by knowing what I
need for the stage, for example I need a voltage gain of 20, an input
impedance of 10K, Z out of ?? etc ----
snip
the easiest stages to design. Normaly, I would start off by knowing what I
need for the stage, for example I need a voltage gain of 20, an input
impedance of 10K, Z out of ?? etc ----
snip
I take your point about selecting a BJT for the desired Iq.
After that, my next consideration is in setting the
collector's average Vc, given an Iq. I want to leave 1V for
the dc bias of Ve to stay well above (kT/q)/Iq. And since I
want to keep the BJT unsaturated I also preserve 1V for Vce.
In your 15V rail case, that leaves me 13V for Vc to wander
around in. Half of 13V is 6.5V. Add back in the 2V I'm
saving, and that sets Vc at Iq as 8.5V.
I set the collector resistor to (Vbat-Vc)/Iq. I get 6.5k for
that. What the heck, make it 6.8k. Iq is now 956uA. Oh,
well.
The emitter resistor is easily set to 1/956uA or slightly
more than 1k. Call it 1k. This means Ve will be about
0.956V. Livable.
On the biasing, I start by assuming that about Iq/5 should
flow in the divider. Say 200uA? (You started out thinking
in terms of the thevenin, instead, and a different rule of
thumb for it. I just use the 1/5th rule.)
Assume Vbe about 0.7V, the base should be at 956mV + 700mV or
about 1.66V. Maybe a little less, maybe a little more.
Assume less, hope for a little more. So 1.6V/200uA is 8k and
(15V-1.6V)/200uA is 67k. Let's go for gusto and pick 68k and
8.2k. ;)
Now, I want a gain of 10? I can either bypass the emitter
resistor with another R+C in series across it or I can divide
up the emitter resistor into two pieces in series and bypass
just one of them, leaving the other one active at AC. With
the collector resistor of 6.8k, a gain of 10 would suggest an
AC resistance of 680 ohms in the emitter. To get that from
the 1k DC for the emitter, we put that 680 in series with a
330 and bypass the 330 with a cap sized appropriately for the
lowest frequency of interest to be close to a 'dead short.'
AC impedance is going to be about the thevenin of the base
pair of resistors divided by (1+5/beta) -- the 5 comes from
my 1/5th factor I earlier chose. If I keep that very much
smaller than the beta, it doesn't affect things much... as
you say. The thevenin of 68k and 8.2k is about 7.3k. With a
beta of 100, for example, this drops to about 6950 ohms.
I'll stop at this point and plug it into LTspice with a
2N2222 model they include (who knows if it is 'good'?)
Adding a signal source through a cap to base, I get a gain of
9.6, an average base voltage of 1.58V, average Iq of 921uA,
and a center Vc of 8.74V. AC impedance is computed as 6961
Ohms in LTspice. Pretty close, really.
Now... to the breadboard for a quick DC check. OnSemi
PN2222A just taken from an ammo pack. Collector resistor of
6.800k, emitter resistor 1.008k, base to ground resistor of
8.360k, base to V+ of 69.53k. Measures (rounded):
Vbat = 15.1
Vb = 1.59
Ve = 0.95
Vc = 8.73
I haven't hooked up the signal generator, yet. I'll need to
move upstairs to do that and get the scope fired up. But
that's a quick check of reality.
Now, plugging the Vbat back into LTspice and the real values
of the resistors I used, I get this from LTspice (rounded.)
Vb = 1.59
Ve = 0.94
Vc = 8.8
Which is ... pretty close. (The OnSemi PDF for the part
doesn't include a spice model for it and a search on their
site only comes up with the MMBT2222, so I'm using the
LTspice model for now.)
Jon
Jon Kirwan
Guest
Guest
Sat Feb 13, 2010 2:08 am
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
Quote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Jim Thompson
Guest
Guest
Sat Feb 13, 2010 2:14 am
On Fri, 12 Feb 2010 17:08:57 -0800, Jon Kirwan
<jonk_at_infinitefactors.org> wrote:
Quote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Jon Kirwan
Guest
Guest
Sat Feb 13, 2010 2:35 am
On Fri, 12 Feb 2010 18:14:37 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
Quote:
On Fri, 12 Feb 2010 17:08:57 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
Okay. Slow down.
So how about a simple (non-Wilson, for now) current mirror in
the emitter? It's easy to select a resistor for the other
side of it to set the current. Then an R+C leg can be used
to set the AC gain!
Jon
Jim Thompson
Guest
Guest
Sat Feb 13, 2010 2:47 am
On Fri, 12 Feb 2010 17:35:48 -0800, Jon Kirwan
<jonk_at_infinitefactors.org> wrote:
Quote:
On Fri, 12 Feb 2010 18:14:37 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 17:08:57 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
Okay. Slow down.
So how about a simple (non-Wilson, for now) current mirror in
the emitter? It's easy to select a resistor for the other
side of it to set the current. Then an R+C leg can be used
to set the AC gain!
Jon
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 17:08:57 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
Okay. Slow down.
So how about a simple (non-Wilson, for now) current mirror in
the emitter? It's easy to select a resistor for the other
side of it to set the current. Then an R+C leg can be used
to set the AC gain!
Jon
Go for it. You're doing fine, you're well on your way to learning!
Report back... including those forays where you get burned
(figuratively and actually
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Jim Thompson
Guest
Guest
Sat Feb 13, 2010 3:28 am
On Fri, 12 Feb 2010 18:47:46 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
Quote:
On Fri, 12 Feb 2010 17:35:48 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 18:14:37 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 17:08:57 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
Okay. Slow down.
So how about a simple (non-Wilson, for now) current mirror in
the emitter? It's easy to select a resistor for the other
side of it to set the current. Then an R+C leg can be used
to set the AC gain!
Jon
Go for it. You're doing fine, you're well on your way to learning!
Report back... including those forays where you get burned
(figuratively and actually
...Jim Thompson
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 18:14:37 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 17:08:57 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 14:38:05 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg_at_nospam.com> wrote:
Jim Thompson wrote in message ...
On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg_at_nospam.com> wrote:
big snip -
Son of a gun. Yesterday you couldn't even spell "engineer", now you
are one (;-0
I finally did something right? Wow!!!
Actually you found the "art" part needed to rough-in a design. Now go
back and fix the flaws
...Jim Thompson
One improvement is to boostrap from emitter to base divider
and use a resistor from there to the BJT base, with the
signal tying in directly to the base via the cap.
Jon
Don't try to get too exotic too fast... you'll get peaking, or worse,
oscillation, if you don't know what you're doing.
But that's a good thing... try it and learn from it
...Jim Thompson
Okay. Slow down.
So how about a simple (non-Wilson, for now) current mirror in
the emitter? It's easy to select a resistor for the other
side of it to set the current. Then an R+C leg can be used
to set the AC gain!
Jon
Go for it. You're doing fine, you're well on your way to learning!
Report back... including those forays where you get burned
(figuratively and actually
...Jim Thompson
And do the math as you go... so you understand what you're seeing.
I was fortunate, grew up in a radio and TV repair shop, and I was
already math-heavy when I trotted off to MIT... had a Russian battle
axe of a teacher named Evelyn Truchovesky for my first round of
Algebra... she pounded me so good I adopted her way of writing "E" in
my signature... to this day ;-)
Washed dishes first year. Second year onward, tech'd in Woodson,
Jackson, Melcher MHD lab (in Building 20)... invaluable experience!
Learn Laplace short-hand, it'll be invaluable!
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
JosephKK
Guest
Guest
Sat Feb 13, 2010 5:04 am
On Tue, 09 Feb 2010 12:25:27 -0800, Jon Kirwan <jonk_at_infinitefactors.org> wrote:
Quote:
On Tue, 09 Feb 2010 06:49:11 -0500, Bitrex
bitrex_at_de.lete.earthlink.net> wrote:
Jon Kirwan wrote:
On Mon, 08 Feb 2010 22:17:31 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 22:11:51 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 20:49:24 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 20:43:03 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 17:54:13 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Hang a big capacitor across it.
Nice try.
Jon
No, seriously, that solves a bunch of problems.
John
Which problems does a slew-dependent, C*dV/dt bypass current
solve?
Jon
A big cap across the biasing gadget keeps the voltage drop across it
fairly constant, of course. That nukes some of the problems you
referred to. More peak current is available to the output bases, for
example.
What size cap would help with power supply ripple? Seems the
dV/dt is so small that a fair sized cap would be required to
make any difference. Similarly for low frequency amplified
signal out of the VAS. When you say "big," maybe you mean
it.
Ban is suggesting global NFB from output back to input.
You've said as much when you say to apply "lots of NFB." I
don't doubt the sincerity of either of you and I'm certain it
will do a lot. But right now I'm interested in seeing what
can be done right on this local subcircuit and at LF as well
as higher frequencies. Unless someone wants to walk me
through the thinking towards the larger concepts. I'm good
either way, as it's the learning that takes place I'm looking
for. But without such guidance, I need to move along at the
pace I can handle while guiding myself.
Jon
Hey Jon, I found a derivation of the input impedance of the two-resistor
/transistor Vbe multiplier you might be interested in looking at:
http://paginas.fe.up.pt/~fff/eBook/MDA/Mult_Vbe.html
That one takes an approach that I'm not familiar with and
didn't take. I'll have to consider the approach more.
However, I did take a look at the end of it. It says:
R = (R1+(R2||re)) / (1+(1/R1+gm)*(R2||re))
If I understand the value gm, and I may not, it's just 1/re
or else re=1/gm. Basically, just the (kT/q)/Ic I'd mentioned
when I wrote. If that is the case, I used these to see how
that page predicts:
ic=.005
vt=k*300/q
gm=ic/vt
re=1/gm
r1=1000
r2=1000
r2p=r2*re/(r2+re)
and then computed:
(r1+r2p)/(1+(1/r1+gm)*r2p)
and got:
502.5719049 Ohms.
This is so far from my own calculations of about 15.4 Ohms
that I just _had_ to put this into LTspice and test it. To
do that, I simply set up the basic circuit with the two
resistors and BJT and then hooked up a variable current
source to the topside. I set it up as an AC source of 5mA
with peaks of 500uA, and then ran a .TRAN on it and plotted
the upper rail of the structure's voltage. I used a 2N2222
BJT, as well. Convenient, and I have them laying about.
Anyway, so I ran the sims and got 17.44mV, peak to peak.
Divided by the peak to peak current variation of 1mA gives an
apparent R of 17.44 Ohms. My calculations arrived at 15.4
Ohms, or so.
All this could be operator error. I may be operating the web
page you suggested incorrectly, so that the 503 Ohms I get is
because I didn't know what I was plugging in and where. I
may be operating LTspice incorrectly, so that it's results
aren't usable and it's just luck that the numbers worked out
in my favor.
But there it is.
Here is the LTspice file:
Version 4
SHEET 1 880 680
WIRE 128 0 16 0
WIRE 224 0 128 0
WIRE 288 0 224 0
WIRE 128 32 128 0
WIRE 16 112 16 0
WIRE 224 112 224 0
WIRE 128 160 128 112
WIRE 160 160 128 160
WIRE 128 208 128 160
WIRE 16 224 16 192
WIRE 128 320 128 288
WIRE 224 320 224 208
WIRE 224 320 128 320
WIRE 128 336 128 320
FLAG 128 336 0
FLAG 288 0 V_rail
FLAG 16 224 0
SYMBOL npn2 160 112 R0
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL res 112 192 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 112 16 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL current 16 192 R180
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I1
SYMATTR Value SINE(5m 500u 50)
TEXT -76 296 Left 0 !.tran 1
For bypassing purposes the rule of thumb I've always heard is to make
the impedance of the capacitor 1/10th the value of the impedance looking
in to the circuit at the lowest audio frequency.
Well, let's assume that I got lucky and LTspice and I agree
on the figure of about 16 Ohms. With a signal at 20Hz, we
are talking:
C = 1/(2 PI f (R_ac/10)) = 5000uF
Yikes. John L. wasn't kidding when he wrote "big." Luckily,
in steady state it could be a low voltage cap!
Jon
bitrex_at_de.lete.earthlink.net> wrote:
Jon Kirwan wrote:
On Mon, 08 Feb 2010 22:17:31 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 22:11:51 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 20:49:24 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 20:43:03 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 17:54:13 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Hang a big capacitor across it.
Nice try.
Jon
No, seriously, that solves a bunch of problems.
John
Which problems does a slew-dependent, C*dV/dt bypass current
solve?
Jon
A big cap across the biasing gadget keeps the voltage drop across it
fairly constant, of course. That nukes some of the problems you
referred to. More peak current is available to the output bases, for
example.
What size cap would help with power supply ripple? Seems the
dV/dt is so small that a fair sized cap would be required to
make any difference. Similarly for low frequency amplified
signal out of the VAS. When you say "big," maybe you mean
it.
Ban is suggesting global NFB from output back to input.
You've said as much when you say to apply "lots of NFB." I
don't doubt the sincerity of either of you and I'm certain it
will do a lot. But right now I'm interested in seeing what
can be done right on this local subcircuit and at LF as well
as higher frequencies. Unless someone wants to walk me
through the thinking towards the larger concepts. I'm good
either way, as it's the learning that takes place I'm looking
for. But without such guidance, I need to move along at the
pace I can handle while guiding myself.
Jon
Hey Jon, I found a derivation of the input impedance of the two-resistor
/transistor Vbe multiplier you might be interested in looking at:
http://paginas.fe.up.pt/~fff/eBook/MDA/Mult_Vbe.html
That one takes an approach that I'm not familiar with and
didn't take. I'll have to consider the approach more.
However, I did take a look at the end of it. It says:
R = (R1+(R2||re)) / (1+(1/R1+gm)*(R2||re))
If I understand the value gm, and I may not, it's just 1/re
or else re=1/gm. Basically, just the (kT/q)/Ic I'd mentioned
when I wrote. If that is the case, I used these to see how
that page predicts:
ic=.005
vt=k*300/q
gm=ic/vt
re=1/gm
r1=1000
r2=1000
r2p=r2*re/(r2+re)
and then computed:
(r1+r2p)/(1+(1/r1+gm)*r2p)
and got:
502.5719049 Ohms.
This is so far from my own calculations of about 15.4 Ohms
that I just _had_ to put this into LTspice and test it. To
do that, I simply set up the basic circuit with the two
resistors and BJT and then hooked up a variable current
source to the topside. I set it up as an AC source of 5mA
with peaks of 500uA, and then ran a .TRAN on it and plotted
the upper rail of the structure's voltage. I used a 2N2222
BJT, as well. Convenient, and I have them laying about.
Anyway, so I ran the sims and got 17.44mV, peak to peak.
Divided by the peak to peak current variation of 1mA gives an
apparent R of 17.44 Ohms. My calculations arrived at 15.4
Ohms, or so.
All this could be operator error. I may be operating the web
page you suggested incorrectly, so that the 503 Ohms I get is
because I didn't know what I was plugging in and where. I
may be operating LTspice incorrectly, so that it's results
aren't usable and it's just luck that the numbers worked out
in my favor.
But there it is.
Here is the LTspice file:
Version 4
SHEET 1 880 680
WIRE 128 0 16 0
WIRE 224 0 128 0
WIRE 288 0 224 0
WIRE 128 32 128 0
WIRE 16 112 16 0
WIRE 224 112 224 0
WIRE 128 160 128 112
WIRE 160 160 128 160
WIRE 128 208 128 160
WIRE 16 224 16 192
WIRE 128 320 128 288
WIRE 224 320 224 208
WIRE 224 320 128 320
WIRE 128 336 128 320
FLAG 128 336 0
FLAG 288 0 V_rail
FLAG 16 224 0
SYMBOL npn2 160 112 R0
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL res 112 192 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 112 16 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL current 16 192 R180
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I1
SYMATTR Value SINE(5m 500u 50)
TEXT -76 296 Left 0 !.tran 1
For bypassing purposes the rule of thumb I've always heard is to make
the impedance of the capacitor 1/10th the value of the impedance looking
in to the circuit at the lowest audio frequency.
Well, let's assume that I got lucky and LTspice and I agree
on the figure of about 16 Ohms. With a signal at 20Hz, we
are talking:
C = 1/(2 PI f (R_ac/10)) = 5000uF
Yikes. John L. wasn't kidding when he wrote "big." Luckily,
in steady state it could be a low voltage cap!
Jon
That is substantially larger than what i have seen in commercial
audio amplifiers (about 5X to 25X), but not particularly surprising.
Jon Kirwan
Guest
Guest
Sat Feb 13, 2010 6:23 am
On Fri, 12 Feb 2010 20:04:36 -0800,
"JosephKK"<quiettechblue_at_yahoo.com> wrote:
Quote:
snip of discussion about a 5000uF cap across a Vbe multiplier
That is substantially larger than what i have seen in commercial
audio amplifiers (about 5X to 25X), but not particularly surprising.
That is substantially larger than what i have seen in commercial
audio amplifiers (about 5X to 25X), but not particularly surprising.
I like the idea of first making the function blocks
themselves better behaved.
Jon
Martin Montonion
Guest
Guest
Sat Feb 13, 2010 2:25 pm
JosephKK wrote:
Quote:
On Tue, 09 Feb 2010 12:25:27 -0800, Jon Kirwan <jonk_at_infinitefactors.org
wrote:
On Tue, 09 Feb 2010 06:49:11 -0500, Bitrex
bitrex_at_de.lete.earthlink.net> wrote:
Jon Kirwan wrote:
On Mon, 08 Feb 2010 22:17:31 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 22:11:51 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 20:49:24 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 20:43:03 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 17:54:13 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Hang a big capacitor across it.
Nice try.
Jon
No, seriously, that solves a bunch of problems.
John
Which problems does a slew-dependent, C*dV/dt bypass current
solve?
Jon
A big cap across the biasing gadget keeps the voltage drop across it
fairly constant, of course. That nukes some of the problems you
referred to. More peak current is available to the output bases, for
example.
What size cap would help with power supply ripple? Seems the
dV/dt is so small that a fair sized cap would be required to
make any difference. Similarly for low frequency amplified
signal out of the VAS. When you say "big," maybe you mean
it.
Ban is suggesting global NFB from output back to input.
You've said as much when you say to apply "lots of NFB." I
don't doubt the sincerity of either of you and I'm certain it
will do a lot. But right now I'm interested in seeing what
can be done right on this local subcircuit and at LF as well
as higher frequencies. Unless someone wants to walk me
through the thinking towards the larger concepts. I'm good
either way, as it's the learning that takes place I'm looking
for. But without such guidance, I need to move along at the
pace I can handle while guiding myself.
Jon
Hey Jon, I found a derivation of the input impedance of the two-resistor
/transistor Vbe multiplier you might be interested in looking at:
http://paginas.fe.up.pt/~fff/eBook/MDA/Mult_Vbe.html
That one takes an approach that I'm not familiar with and
didn't take. I'll have to consider the approach more.
However, I did take a look at the end of it. It says:
R = (R1+(R2||re)) / (1+(1/R1+gm)*(R2||re))
If I understand the value gm, and I may not, it's just 1/re
or else re=1/gm. Basically, just the (kT/q)/Ic I'd mentioned
when I wrote. If that is the case, I used these to see how
that page predicts:
ic=.005
vt=k*300/q
gm=ic/vt
re=1/gm
r1=1000
r2=1000
r2p=r2*re/(r2+re)
and then computed:
(r1+r2p)/(1+(1/r1+gm)*r2p)
and got:
502.5719049 Ohms.
This is so far from my own calculations of about 15.4 Ohms
that I just _had_ to put this into LTspice and test it. To
do that, I simply set up the basic circuit with the two
resistors and BJT and then hooked up a variable current
source to the topside. I set it up as an AC source of 5mA
with peaks of 500uA, and then ran a .TRAN on it and plotted
the upper rail of the structure's voltage. I used a 2N2222
BJT, as well. Convenient, and I have them laying about.
Anyway, so I ran the sims and got 17.44mV, peak to peak.
Divided by the peak to peak current variation of 1mA gives an
apparent R of 17.44 Ohms. My calculations arrived at 15.4
Ohms, or so.
All this could be operator error. I may be operating the web
page you suggested incorrectly, so that the 503 Ohms I get is
because I didn't know what I was plugging in and where. I
may be operating LTspice incorrectly, so that it's results
aren't usable and it's just luck that the numbers worked out
in my favor.
But there it is.
Here is the LTspice file:
Version 4
SHEET 1 880 680
WIRE 128 0 16 0
WIRE 224 0 128 0
WIRE 288 0 224 0
WIRE 128 32 128 0
WIRE 16 112 16 0
WIRE 224 112 224 0
WIRE 128 160 128 112
WIRE 160 160 128 160
WIRE 128 208 128 160
WIRE 16 224 16 192
WIRE 128 320 128 288
WIRE 224 320 224 208
WIRE 224 320 128 320
WIRE 128 336 128 320
FLAG 128 336 0
FLAG 288 0 V_rail
FLAG 16 224 0
SYMBOL npn2 160 112 R0
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL res 112 192 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 112 16 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL current 16 192 R180
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I1
SYMATTR Value SINE(5m 500u 50)
TEXT -76 296 Left 0 !.tran 1
For bypassing purposes the rule of thumb I've always heard is to make
the impedance of the capacitor 1/10th the value of the impedance looking
in to the circuit at the lowest audio frequency.
Well, let's assume that I got lucky and LTspice and I agree
on the figure of about 16 Ohms. With a signal at 20Hz, we
are talking:
C = 1/(2 PI f (R_ac/10)) = 5000uF
Yikes. John L. wasn't kidding when he wrote "big." Luckily,
in steady state it could be a low voltage cap!
Jon
That is substantially larger than what i have seen in commercial
audio amplifiers (about 5X to 25X), but not particularly surprising.
wrote:
On Tue, 09 Feb 2010 06:49:11 -0500, Bitrex
bitrex_at_de.lete.earthlink.net> wrote:
Jon Kirwan wrote:
On Mon, 08 Feb 2010 22:17:31 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 22:11:51 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 20:49:24 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Mon, 08 Feb 2010 20:43:03 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Mon, 08 Feb 2010 17:54:13 -0800, John Larkin
jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Hang a big capacitor across it.
Nice try.
Jon
No, seriously, that solves a bunch of problems.
John
Which problems does a slew-dependent, C*dV/dt bypass current
solve?
Jon
A big cap across the biasing gadget keeps the voltage drop across it
fairly constant, of course. That nukes some of the problems you
referred to. More peak current is available to the output bases, for
example.
What size cap would help with power supply ripple? Seems the
dV/dt is so small that a fair sized cap would be required to
make any difference. Similarly for low frequency amplified
signal out of the VAS. When you say "big," maybe you mean
it.
Ban is suggesting global NFB from output back to input.
You've said as much when you say to apply "lots of NFB." I
don't doubt the sincerity of either of you and I'm certain it
will do a lot. But right now I'm interested in seeing what
can be done right on this local subcircuit and at LF as well
as higher frequencies. Unless someone wants to walk me
through the thinking towards the larger concepts. I'm good
either way, as it's the learning that takes place I'm looking
for. But without such guidance, I need to move along at the
pace I can handle while guiding myself.
Jon
Hey Jon, I found a derivation of the input impedance of the two-resistor
/transistor Vbe multiplier you might be interested in looking at:
http://paginas.fe.up.pt/~fff/eBook/MDA/Mult_Vbe.html
That one takes an approach that I'm not familiar with and
didn't take. I'll have to consider the approach more.
However, I did take a look at the end of it. It says:
R = (R1+(R2||re)) / (1+(1/R1+gm)*(R2||re))
If I understand the value gm, and I may not, it's just 1/re
or else re=1/gm. Basically, just the (kT/q)/Ic I'd mentioned
when I wrote. If that is the case, I used these to see how
that page predicts:
ic=.005
vt=k*300/q
gm=ic/vt
re=1/gm
r1=1000
r2=1000
r2p=r2*re/(r2+re)
and then computed:
(r1+r2p)/(1+(1/r1+gm)*r2p)
and got:
502.5719049 Ohms.
This is so far from my own calculations of about 15.4 Ohms
that I just _had_ to put this into LTspice and test it. To
do that, I simply set up the basic circuit with the two
resistors and BJT and then hooked up a variable current
source to the topside. I set it up as an AC source of 5mA
with peaks of 500uA, and then ran a .TRAN on it and plotted
the upper rail of the structure's voltage. I used a 2N2222
BJT, as well. Convenient, and I have them laying about.
Anyway, so I ran the sims and got 17.44mV, peak to peak.
Divided by the peak to peak current variation of 1mA gives an
apparent R of 17.44 Ohms. My calculations arrived at 15.4
Ohms, or so.
All this could be operator error. I may be operating the web
page you suggested incorrectly, so that the 503 Ohms I get is
because I didn't know what I was plugging in and where. I
may be operating LTspice incorrectly, so that it's results
aren't usable and it's just luck that the numbers worked out
in my favor.
But there it is.
Here is the LTspice file:
Version 4
SHEET 1 880 680
WIRE 128 0 16 0
WIRE 224 0 128 0
WIRE 288 0 224 0
WIRE 128 32 128 0
WIRE 16 112 16 0
WIRE 224 112 224 0
WIRE 128 160 128 112
WIRE 160 160 128 160
WIRE 128 208 128 160
WIRE 16 224 16 192
WIRE 128 320 128 288
WIRE 224 320 224 208
WIRE 224 320 128 320
WIRE 128 336 128 320
FLAG 128 336 0
FLAG 288 0 V_rail
FLAG 16 224 0
SYMBOL npn2 160 112 R0
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL res 112 192 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 112 16 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL current 16 192 R180
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName I1
SYMATTR Value SINE(5m 500u 50)
TEXT -76 296 Left 0 !.tran 1
For bypassing purposes the rule of thumb I've always heard is to make
the impedance of the capacitor 1/10th the value of the impedance looking
in to the circuit at the lowest audio frequency.
Well, let's assume that I got lucky and LTspice and I agree
on the figure of about 16 Ohms. With a signal at 20Hz, we
are talking:
C = 1/(2 PI f (R_ac/10)) = 5000uF
Yikes. John L. wasn't kidding when he wrote "big." Luckily,
in steady state it could be a low voltage cap!
Jon
That is substantially larger than what i have seen in commercial
audio amplifiers (about 5X to 25X), but not particularly surprising.
And there are very good reasons for limiting the size of capacitors in
commercial designs. Even if the increased volume and cost is not an
issue, reliability will go down for a bigger cap.
--
Cool links for aspiring physicists, from a Nobel laureate:
http://www.phys.uu.nl/~thooft/theorist.html
Jon Kirwan
Guest
Guest
Sat Feb 13, 2010 8:40 pm
On Sat, 13 Feb 2010 09:09:39 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
Quote:
On Fri, 12 Feb 2010 19:05:46 -0800, Jon Kirwan
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 19:28:51 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
[snip]
Learn Laplace short-hand, it'll be invaluable!
...Jim Thompson
I'm gradually getting more comfortable with Laplace, as I
continue to work more problems. It is an especially nifty
way to solve some differential equations, which is what it
was designed to do, I think.
Jon
Actually, shorthand Laplace was created by none other than Oliver
Heaviside: http://en.wikipedia.org/wiki/Oliver_Heaviside
...Jim Thompson
jonk_at_infinitefactors.org> wrote:
On Fri, 12 Feb 2010 19:28:51 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote:
[snip]
Learn Laplace short-hand, it'll be invaluable!
...Jim Thompson
I'm gradually getting more comfortable with Laplace, as I
continue to work more problems. It is an especially nifty
way to solve some differential equations, which is what it
was designed to do, I think.
Jon
Actually, shorthand Laplace was created by none other than Oliver
Heaviside: http://en.wikipedia.org/wiki/Oliver_Heaviside
...Jim Thompson
Now that's an impressive man. Thanks! I'll dig in!
Jon
JosephKK
Guest
Guest
Sun Feb 14, 2010 1:48 am
On Tue, 9 Feb 2010 18:58:36 -0800, "Bob Monsen" <rcmonsen_at_gmail.com> wrote:
Quote:
"Jim Thompson" <To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote in
message news:4604n5lppq5jocclt3si1gdjveeu345den_at_4ax.com...
Something smelly there. I'll try it tomorrow... the Moo Goo Gai Pan
I love to cook with wine. Sometimes I even put it in the food.
The original is from EDN, Oct 22, 2009, page 45. "Class B amplifier has
automatic bias".
Regards,
Bob Monsen
message news:4604n5lppq5jocclt3si1gdjveeu345den_at_4ax.com...
Something smelly there. I'll try it tomorrow... the Moo Goo Gai Pan
I love to cook with wine. Sometimes I even put it in the food.
The original is from EDN, Oct 22, 2009, page 45. "Class B amplifier has
automatic bias".
Regards,
Bob Monsen
I found the original on the 'net
http://www.edn.com/article/CA6702272.html?text=%22Class+B+amplifier+has++automatic+bias%22
Something fishy indeed.
JosephKK
Guest
Guest
Sun Feb 14, 2010 1:49 am
On Tue, 9 Feb 2010 18:10:10 -0600, "Tim Williams" <tmoranwms_at_charter.net> wrote:
Quote:
"Jim Thompson" <To-Email-Use-The-Envelope-Icon_at_My-Web-Site.com> wrote in
message news:mhr3n5pv3mnp4dlfo1pmvib066vjjovj44_at_4ax.com...
Did something get lost in the ASCII? Otherwise collector-to-collector
as in Q1-Q4 is a no-no... one of those devices will saturate.
It's a current mirror, based on hFE instead of Vbe (yuck!). When Q1 or Q4
saturates, bias current (or op-amp current) is diverted to the output
transistors, driving the load.
Tim
message news:mhr3n5pv3mnp4dlfo1pmvib066vjjovj44_at_4ax.com...
Did something get lost in the ASCII? Otherwise collector-to-collector
as in Q1-Q4 is a no-no... one of those devices will saturate.
It's a current mirror, based on hFE instead of Vbe (yuck!). When Q1 or Q4
saturates, bias current (or op-amp current) is diverted to the output
transistors, driving the load.
Tim
No, i don't think it is even that good.
JosephKK
Guest
Guest
Sun Feb 14, 2010 2:34 am
On Thu, 11 Feb 2010 19:37:27 -0800, Jon Kirwan <jonk_at_infinitefactors.org> wrote:
Quote:
On Thu, 11 Feb 2010 19:23:04 -0800 (PST), George Herold
ggherold_at_gmail.com> wrote:
On Feb 11, 3:24 am, Jon Kirwan <j...@infinitefactors.org> wrote:
On Wed, 10 Feb 2010 19:55:44 -0800 (PST), George Herold
ggher...@gmail.com> wrote:
I'm perhaps more of a novice than you...
Somehow, I doubt that. I barely rate "hobbyist."
but I find opamp circuits complicated enough....
Don't sweat it. While some opamps leave _some_ issues nearly
ignorable, there is always some tough problem at that scale
that makes it non-trivial and interesting to work on, I
imagine. Each macroscale view has it's own complexity.
Telescoping levels, where the complexity at one stage doesn't
take away from interesting complexity at another level.
(I would say more but I'm keeping in mind your warning about
long-windedness and will now muzzle myself.)
And tend to stick transistors
only on the edges of things. (Mostly on the output side... on the
input you have to 'know more' than the guys who designed the opamp..
hard to do for a novice.)
I do the same things except that I enjoy math and BJTs give
me an excuse, perhaps. Maybe that's the only difference.
I guess if I was designing an audio amp I'd figure on an opamp driving
some sort of FET output stage. The question of how to bias the output
stage is interesting. And also of how all the NFB works.
Might as well just get a power opamp like the OPA502 and be
done with it. Give it two rails, feed the input, and just
drive the hell out of a speaker. Or get two of them and do a
bridge amplifier. But where is the enjoyment in that? Or
the learning? Someone else already did most of the fun stuff
and there's nothing really left to do except some hook up and
heat sinking. It's not at all satisfying to me, anyway.
An audio amplifier is basically a power opamp. Using an
opamp to make one feels to me like building a car by first
buying a car without the tires, selecting and installing some
tires, and then saying you designed and built yourself a car.
Jon
Big Grins!
Yeah I applaud your effort, I wait for further posts.
For me, I’m building electronics to either detect something or drive
something that’s detecting something. So the fun is in making good
detectors or drivers.
George H.
Well, I am wanting, eventually, to build something I need.
Something I cannot buy in the market because the need is
unique.
This divides into two parts. Design and build. Since the
item is unique, I can't just go out and buy it. And getting
the features I need cannot just be "hacked" into existing
designs without at least knowing _some_ stuff, first. I
might as well turn the "design" part into a fair learning
experience, as a separate project of its own. Get past that
and when it comes time to build what I want I'll be able to
build on what I learned and add what I need and then do a
modest hobbyist level whack at actually making what I want to
make.
If someone else were to do this for me (hire a designer),
they'd get all the fun of learning on the job and taking my
money with it. They get the money, they get to further their
own education, and I get a tool. One tool. Once. Next
time, I get to pay someone else to learn for me.
It almost feels like paying someone to go do your exercising
for you. No satisfaction and no weight loss. They get all
the _real_ benefits.
Part of the fun isn't the destination itself but it is what
you see and enjoy while getting there, too. You take a plane
when all you need is to "get there" quick, but you drive when
you want to enjoy stops along the way. I used to fly to
Burbank every week for a year and a half. Slept in a hotel
for 3 nights a week, worked day and night in between, flew
home. Barely saw anything but hotel room walls, cubical
walls, a few cement roads, pollution so thick you couldn't
see the Burbank hills from the Lockheed center, and not much
else. The destination was important, of course. Paid the
bills and I enjoyed the work, too. But there is a lot more
to see in the 1000 miles from here to there.
Anyway, I'm driving this time, not flying.
Besides, I'd rather _keep_ the money and _keep_ the education
for myself. That way it pays off, again and again.
Jon
ggherold_at_gmail.com> wrote:
On Feb 11, 3:24 am, Jon Kirwan <j...@infinitefactors.org> wrote:
On Wed, 10 Feb 2010 19:55:44 -0800 (PST), George Herold
ggher...@gmail.com> wrote:
I'm perhaps more of a novice than you...
Somehow, I doubt that. I barely rate "hobbyist."
but I find opamp circuits complicated enough....
Don't sweat it. While some opamps leave _some_ issues nearly
ignorable, there is always some tough problem at that scale
that makes it non-trivial and interesting to work on, I
imagine. Each macroscale view has it's own complexity.
Telescoping levels, where the complexity at one stage doesn't
take away from interesting complexity at another level.
(I would say more but I'm keeping in mind your warning about
long-windedness and will now muzzle myself.)
And tend to stick transistors
only on the edges of things. (Mostly on the output side... on the
input you have to 'know more' than the guys who designed the opamp..
hard to do for a novice.)
I do the same things except that I enjoy math and BJTs give
me an excuse, perhaps. Maybe that's the only difference.
I guess if I was designing an audio amp I'd figure on an opamp driving
some sort of FET output stage. The question of how to bias the output
stage is interesting. And also of how all the NFB works.
Might as well just get a power opamp like the OPA502 and be
done with it. Give it two rails, feed the input, and just
drive the hell out of a speaker. Or get two of them and do a
bridge amplifier. But where is the enjoyment in that? Or
the learning? Someone else already did most of the fun stuff
and there's nothing really left to do except some hook up and
heat sinking. It's not at all satisfying to me, anyway.
An audio amplifier is basically a power opamp. Using an
opamp to make one feels to me like building a car by first
buying a car without the tires, selecting and installing some
tires, and then saying you designed and built yourself a car.
Jon
Big Grins!
Yeah I applaud your effort, I wait for further posts.
For me, I’m building electronics to either detect something or drive
something that’s detecting something. So the fun is in making good
detectors or drivers.
George H.
Well, I am wanting, eventually, to build something I need.
Something I cannot buy in the market because the need is
unique.
This divides into two parts. Design and build. Since the
item is unique, I can't just go out and buy it. And getting
the features I need cannot just be "hacked" into existing
designs without at least knowing _some_ stuff, first. I
might as well turn the "design" part into a fair learning
experience, as a separate project of its own. Get past that
and when it comes time to build what I want I'll be able to
build on what I learned and add what I need and then do a
modest hobbyist level whack at actually making what I want to
make.
If someone else were to do this for me (hire a designer),
they'd get all the fun of learning on the job and taking my
money with it. They get the money, they get to further their
own education, and I get a tool. One tool. Once. Next
time, I get to pay someone else to learn for me.
It almost feels like paying someone to go do your exercising
for you. No satisfaction and no weight loss. They get all
the _real_ benefits.
Part of the fun isn't the destination itself but it is what
you see and enjoy while getting there, too. You take a plane
when all you need is to "get there" quick, but you drive when
you want to enjoy stops along the way. I used to fly to
Burbank every week for a year and a half. Slept in a hotel
for 3 nights a week, worked day and night in between, flew
home. Barely saw anything but hotel room walls, cubical
walls, a few cement roads, pollution so thick you couldn't
see the Burbank hills from the Lockheed center, and not much
else. The destination was important, of course. Paid the
bills and I enjoyed the work, too. But there is a lot more
to see in the 1000 miles from here to there.
Anyway, I'm driving this time, not flying.
Besides, I'd rather _keep_ the money and _keep_ the education
for myself. That way it pays off, again and again.
Jon
Spot on. That is why i am rebuilding my tinkering kit.
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