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John Larkin
Guest
Guest
Sat Feb 06, 2010 6:02 am
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
<tmoranwms_at_charter.net> wrote:
Quote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com...
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com...
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
Tim Williams
Guest
Guest
Sun Feb 07, 2010 2:42 am
"JosephKK" <quiettechblue_at_yahoo.com> wrote in message
news:7anom5d66k5nn9k3epml4tm5q4hbuelh9g_at_4ax.com...
Quote:
Do you need continuously adjustable or can you live with discrete steps
on the current ratio?
on the current ratio?
Continuous, or sufficiently continuous (>= 8 bits?).
I suppose an alternate formulation might be, if it can't be varied reliably
over a wide range, then it could be varied over a small dither range while
the switching handles the wide range, but that would quickly get ugly..
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
JosephKK
Guest
Guest
Sun Feb 07, 2010 4:45 am
On Fri, 05 Feb 2010 21:02:46 -0800, John Larkin <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com....
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com....
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
John Larkin
Guest
Guest
Sun Feb 07, 2010 5:01 am
On Sat, 06 Feb 2010 19:45:38 -0800,
"JosephKK"<quiettechblue_at_yahoo.com> wrote:
Quote:
On Fri, 05 Feb 2010 21:02:46 -0800, John Larkin <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com...
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com...
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
This config is ideal for driving current into inductive loads, like
MRI coils. The inherently high output impedance makes closed-loop
dynamics mostly independent of load.
For audio, where you want a low output impedance, it's not ideal. The
fix is to apply massive negative feedback, which requires tons of GBW
to waste at higher frequencies. That was probably hard to do in 1965.
Got a schematic?
John
Jim Thompson
Guest
Guest
Sun Feb 07, 2010 5:21 pm
On Sat, 06 Feb 2010 19:45:38 -0800,
"JosephKK"<quiettechblue_at_yahoo.com> wrote:
Quote:
On Fri, 05 Feb 2010 21:02:46 -0800, John Larkin <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com...
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com...
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
MC1524, actually was an I/C plus a 2N2222 and a 2N2906.
...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
Mon Feb 08, 2010 6:38 am
On Sat, 6 Feb 2010 19:42:35 -0600, "Tim Williams" <tmoranwms_at_charter.net> wrote:
Quote:
"JosephKK" <quiettechblue_at_yahoo.com> wrote in message
news:7anom5d66k5nn9k3epml4tm5q4hbuelh9g_at_4ax.com...
Do you need continuously adjustable or can you live with discrete steps
on the current ratio?
Continuous, or sufficiently continuous (>= 8 bits?).
I suppose an alternate formulation might be, if it can't be varied reliably
over a wide range, then it could be varied over a small dither range while
the switching handles the wide range, but that would quickly get ugly..
Tim
news:7anom5d66k5nn9k3epml4tm5q4hbuelh9g_at_4ax.com...
Do you need continuously adjustable or can you live with discrete steps
on the current ratio?
Continuous, or sufficiently continuous (>= 8 bits?).
I suppose an alternate formulation might be, if it can't be varied reliably
over a wide range, then it could be varied over a small dither range while
the switching handles the wide range, but that would quickly get ugly..
Tim
For fully continuous i would look at a application of a Gilbert cell multiplier.
There are some relatively exposed Gilbert cell ICs available.
For a steppy solution an 8 or more bit (multiplying) current diverting DAC.
Though i am not sure if a DAC will work well over two decades of reference
current, you may have to subrange to two or three steps (that may overlap).
Both solutions will require some appropriate scaling before or after or both.
JosephKK
Guest
Guest
Mon Feb 08, 2010 6:43 am
On Sat, 06 Feb 2010 20:01:31 -0800, John Larkin <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Sat, 06 Feb 2010 19:45:38 -0800,
"JosephKK"<quiettechblue_at_yahoo.com> wrote:
On Fri, 05 Feb 2010 21:02:46 -0800, John Larkin <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com....
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
This config is ideal for driving current into inductive loads, like
MRI coils. The inherently high output impedance makes closed-loop
dynamics mostly independent of load.
For audio, where you want a low output impedance, it's not ideal. The
fix is to apply massive negative feedback, which requires tons of GBW
to waste at higher frequencies. That was probably hard to do in 1965.
Got a schematic?
John
"JosephKK"<quiettechblue_at_yahoo.com> wrote:
On Fri, 05 Feb 2010 21:02:46 -0800, John Larkin <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 5 Feb 2010 11:21:05 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"whit3rd" <whit3rd_at_gmail.com> wrote in message
news:152e5f52-6af1-4cb3-aa39-0ecf74e30db1_at_q4g2000yqm.googlegroups.com....
The schemes John Larkin gave are unipolar, and 'current from +V or -V'
sounds like bipolar to me.
No, it's unipolar, I meant the currents are sourced from the +V rail, or
sunk into the -V rail.
Your circuit reminds me of,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Current_Amplifer.gif
which isn't to be left alone on the breadboard unless the transistors are on
a fairly large heatsink. ;-)
Tim
Using the opamp rail currents gives essentially perfect crossover
behavior. At zero signal, both mirrors run at their Iq. As you apply
signal in one direction, one mirror current goes up and the other
stays at Iq. That's different from most class AB stages, where as one
side conducts, the other is turned off... which can lead to weird
transient distortions.
John
And to think i cribbed that trick from datasheets and application
notes in 1965 to build my first self designed stereo.
This config is ideal for driving current into inductive loads, like
MRI coils. The inherently high output impedance makes closed-loop
dynamics mostly independent of load.
For audio, where you want a low output impedance, it's not ideal. The
fix is to apply massive negative feedback, which requires tons of GBW
to waste at higher frequencies. That was probably hard to do in 1965.
Got a schematic?
John
I doubt if i still have the schematic. I should be able to do a fresh
instance with current parts. In a couple of days as an LTspice file OK.
The parts to the original may be unobtainium now.
Tim Williams
Guest
Guest
Mon Feb 08, 2010 8:19 pm
"JosephKK" <quiettechblue_at_yahoo.com> wrote in message
news:8q7vm5hrekhi5rq86ffrbflv655tjg45nm_at_4ax.com...
Quote:
For fully continuous i would look at a application of a Gilbert cell
multiplier.
There are some relatively exposed Gilbert cell ICs available.
multiplier.
There are some relatively exposed Gilbert cell ICs available.
Hmm. I have some MC1496's laying around, that's halfway there. Or use a
TIA. I wouldn't need four quadrants, one would be enough. That would even
suggest a JFET. The problem is making the 0.1 to 10 ratio repeatable with
an output from 50nA to 50mA (maybe not 50 on the highest range, I could
settle for 5mA max.). That means putting the programming current into the
tail is tricky (a regular current mirror would do okay), and the output can
only be varied from 1 to 0.01 instead of 0.1 to 10 times (well, close
enough).
In this circuit,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
I did something kinda similar, but more simply adjustable, and obviously the
ratio is fixed. As I recall, duty cycle was fairly consistent across the
range, and at cutoff it was on the order of nanoamps through the 2N440x's.
If the multiplier's ratio is constant for a given differential voltage
offset (which will have to be temperature compensated, but that would simply
mean sourcing that offset voltage from a diode), then this might work fairly
well.
Thanks, this is something to think about.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
John Larkin
Guest
Guest
Mon Feb 08, 2010 9:58 pm
On Mon, 8 Feb 2010 13:19:43 -0600, "Tim Williams"
<tmoranwms_at_charter.net> wrote:
Quote:
"JosephKK" <quiettechblue_at_yahoo.com> wrote in message
news:8q7vm5hrekhi5rq86ffrbflv655tjg45nm_at_4ax.com...
For fully continuous i would look at a application of a Gilbert cell
multiplier.
There are some relatively exposed Gilbert cell ICs available.
Hmm. I have some MC1496's laying around, that's halfway there. Or use a
TIA. I wouldn't need four quadrants, one would be enough. That would even
suggest a JFET. The problem is making the 0.1 to 10 ratio repeatable with
an output from 50nA to 50mA (maybe not 50 on the highest range, I could
settle for 5mA max.). That means putting the programming current into the
tail is tricky (a regular current mirror would do okay), and the output can
only be varied from 1 to 0.01 instead of 0.1 to 10 times (well, close
enough).
In this circuit,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
news:8q7vm5hrekhi5rq86ffrbflv655tjg45nm_at_4ax.com...
For fully continuous i would look at a application of a Gilbert cell
multiplier.
There are some relatively exposed Gilbert cell ICs available.
Hmm. I have some MC1496's laying around, that's halfway there. Or use a
TIA. I wouldn't need four quadrants, one would be enough. That would even
suggest a JFET. The problem is making the 0.1 to 10 ratio repeatable with
an output from 50nA to 50mA (maybe not 50 on the highest range, I could
settle for 5mA max.). That means putting the programming current into the
tail is tricky (a regular current mirror would do okay), and the output can
only be varied from 1 to 0.01 instead of 0.1 to 10 times (well, close
enough).
In this circuit,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
John
Tim Williams
Guest
Guest
Mon Feb 08, 2010 10:26 pm
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
Quote:
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Jim Thompson
Guest
Guest
Mon Feb 08, 2010 10:29 pm
On Mon, 08 Feb 2010 12:58:04 -0800, John Larkin
<jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Mon, 8 Feb 2010 13:19:43 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"JosephKK" <quiettechblue_at_yahoo.com> wrote in message
news:8q7vm5hrekhi5rq86ffrbflv655tjg45nm_at_4ax.com...
For fully continuous i would look at a application of a Gilbert cell
multiplier.
There are some relatively exposed Gilbert cell ICs available.
Hmm. I have some MC1496's laying around, that's halfway there. Or use a
TIA. I wouldn't need four quadrants, one would be enough. That would even
suggest a JFET. The problem is making the 0.1 to 10 ratio repeatable with
an output from 50nA to 50mA (maybe not 50 on the highest range, I could
settle for 5mA max.). That means putting the programming current into the
tail is tricky (a regular current mirror would do okay), and the output can
only be varied from 1 to 0.01 instead of 0.1 to 10 times (well, close
enough).
In this circuit,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
John
tmoranwms_at_charter.net> wrote:
"JosephKK" <quiettechblue_at_yahoo.com> wrote in message
news:8q7vm5hrekhi5rq86ffrbflv655tjg45nm_at_4ax.com...
For fully continuous i would look at a application of a Gilbert cell
multiplier.
There are some relatively exposed Gilbert cell ICs available.
Hmm. I have some MC1496's laying around, that's halfway there. Or use a
TIA. I wouldn't need four quadrants, one would be enough. That would even
suggest a JFET. The problem is making the 0.1 to 10 ratio repeatable with
an output from 50nA to 50mA (maybe not 50 on the highest range, I could
settle for 5mA max.). That means putting the programming current into the
tail is tricky (a regular current mirror would do okay), and the output can
only be varied from 1 to 0.01 instead of 0.1 to 10 times (well, close
enough).
In this circuit,
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
John
Certainly worth saving. You might learn something from those of us
who can _really_ design at the device level, instead of copying
from...
...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.
John Larkin
Guest
Guest
Mon Feb 08, 2010 10:51 pm
On Mon, 8 Feb 2010 15:26:41 -0600, "Tim Williams"
<tmoranwms_at_charter.net> wrote:
Quote:
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
Let's see how many people can each find one problem.
The most obvious one is the the charge/discharge currents depend on
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
John
Tim Williams
Guest
Guest
Mon Feb 08, 2010 10:53 pm
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:vf11n5hiervl0ukh1o0qett8gsfut726vk_at_4ax.com...
Quote:
The most obvious one is the the charge/discharge currents depend on
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
Well, the duty cycle ended up fairly close to 50% just picking random 440x's
out of the box. No selection, put it together and it worked. Why, were you
expecting 3 PNP's and 2 NPNs if they were selected?
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Spehro Pefhany
Guest
Guest
Mon Feb 08, 2010 11:12 pm
On Mon, 08 Feb 2010 13:51:28 -0800, John Larkin
<jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Mon, 8 Feb 2010 15:26:41 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
Let's see how many people can each find one problem.
The most obvious one is the the charge/discharge currents depend on
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
John
tmoranwms_at_charter.net> wrote:
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
Let's see how many people can each find one problem.
The most obvious one is the the charge/discharge currents depend on
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
John
? The top mirror gives +I, the bottom mirror gives -2*I, where I is
the current through the NPN emitter follower.
When the 2N4403 (emitter connected to +
is "on" you get +I (cause it
conducts the -2I away through the diode), when it is off you get a net
of -I.
I got a crap mark in Uni for a circuit much like this one, because the
TA didn't understand it. 8-(
Jim Thompson
Guest
Guest
Mon Feb 08, 2010 11:12 pm
On Mon, 08 Feb 2010 13:51:28 -0800, John Larkin
<jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Mon, 8 Feb 2010 15:26:41 -0600, "Tim Williams"
tmoranwms_at_charter.net> wrote:
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
Let's see how many people can each find one problem.
The most obvious one is the the charge/discharge currents depend on
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
John
tmoranwms_at_charter.net> wrote:
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:3ju0n51fhfrj2pukuet0obtibm2p7lnmu3_at_4ax.com...
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif
That circuit is so astoundingly bad that it's worth saving.
Bad for what?
It has an unusually wide range, as discrete circuits go. On 680pF, I got
from 1Hz to 4.5MHz in a single range. Six decades isn't bad for a 2N440x.
Smaller RF BJT's would go lower, or you could do range switching or more
exotic approaches (leaky photodiode?).
Besides the wide range, what impressed me is the diffamp got the 2N4403
switching in about 20ns, for a balls-out maximum frequency around 35MHz.
Faster transistors would also take this arbitrarily high (the PHEMTs you're
so fond of would probably make a proper RC oscillator in the GHz). Say, do
they even make P type stupidfast transistors, SiGe or otherwise? I remember
they don't bother with P type GaAs or InP since they suck for holes.
I don't remember if, when set at ~10Hz or so, the frequency drifted by a
decade or so when I touched the leftmost transistor. It ought to. I do
remember seeing it change in steps, since I was using a wirewound pot.
Tim
Let's see how many people can each find one problem.
The most obvious one is the the charge/discharge currents depend on
the betas of the upper and lower mirror transistors. That's probably
why there are two PNPs and three NPNs: they were selected to work.
John
There are sufficient "errors" in there to suppose drafting goofs.
...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.
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