Sine generator IC solution?

In article <41FD0BE4.2030700@nospam.com>,
Fred Bloggs <nospam@nospam.com> wrote:

You're not going to do much in the way of a 10:1 tuning range in
Wien bridge- fussy little high Q and amplitude unstable thing
that it is. These days the most practical and high performance
approach, at these frequencies, would be to generate a variable
frequency square wave at fundamental and 100x fundamental which
are then processed by cheap switching tracking filter.
Click to expand...
An 8038-variety is still the easiest approach if
not much better than 1% THD is ok.

Your approach is nifty and could be very handy if
(say) something like a 2-phase sine/cosine was required.

Note that there is a 3-step square-wave approximation
of a sine which has zero third harmonic content, very
useful if going into a low pass filter.

--
Tony Williams.
 
I read in sci.electronics.design that Tony Williams
<tonyw@ledelec.demon.co.uk> wrote (in <4d35e6c072tonyw@ledelec.demon.co.
uk>) about 'Sine generator IC solution?', on Mon, 31 Jan 2005:
You're not going to do much in the way of a 10:1 tuning range in
Wien bridge- fussy little high Q and amplitude unstable thing
that it is.
Click to expand...
The Q of a Wien network is 1/3, not high.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <89rsv0115k75l8mcc0m1gmslgh7qljbpev@4ax.com>)
about 'Sine generator IC solution?', on Mon, 31 Jan 2005:

I should remember that- I just shipped something to there. But mostly I
was struggling with "Heiligenstädterstrasse" on the customs form.
Click to expand...
Holy city street, Batman! (;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
On 29 Jan 2005 15:09:08 -0800, the renowned "dave.harper"
<dave.harper@gmail.com> wrote:

Are there any variable sine generator IC's? I was looking for a single
chip solution, but am not sure if they exist (other than programing a
PIC or similar). The frequency range I'm working with is between 200
and 2000 Hz. Ideally I'd like it to be accurate (or adjustable) to
within 10 Hz.

Thanks in advance!
Dave
Click to expand...
ICL8038, MAX038 can be used to generate sine-like waveforms (made from
triangle waves). That's probably the easiest way for you if you don't
care too much about stability, distortion, or cost.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
"dave.harper" (dave.harper@gmail.com) writes:
mike wrote:
dave.harper wrote:
Are there any variable sine generator IC's? I was looking for a
single
chip solution, but am not sure if they exist (other than programing
a
PIC or similar). The frequency range I'm working with is between
200
and 2000 Hz. Ideally I'd like it to be accurate (or adjustable) to
within 10 Hz.

Thanks in advance!
Dave


Whatchagonnadowithit?

I'm trying to make a radio modem that can be controlled via a PIC.
I've managed to create one that can communicate via RTTY and AMTOR-FEC
(ham radio protocols) at 100 baud, but the waveform looks like the PIC
threw up on the oscope. My software is still able to decode it at 100
baud without a problem, but at higher speeds it's becoming an issue.
So I'm looking for something to create a less nausiating wave form and
would cause less problems for the recieving software to decode at
higher speeds. That's why I'm concerned with the tolerance on the
frequencies... What about a 555 with tightly toleranced resistors and
caps, and a double-integrated output...?

Dave
Click to expand...
But you don't need a 10:1 tuning range. The frequency shift should
be much less. Amateur Teletype originally used 850Hz shift,
specifically 2125Hz and 2975Hz for the two frequencies. When narrow
shift came in, the differential between the frequencies was 170Hz,
using 2125 and 2295Hz as the specific tones.

If this was done at audio frequencies, there'd be an LC oscillator,
and then a capacitor would be switched in for the lower frequency.

Of course, one could get shift by moving the actual frequency of
the transmitter, and this too was done by adding in a capacitor when
the lower frequency was being sent. Of course, doing frequency shift
rather than shifting an audio signal, you had to either use an SSB
receiver to shift the signal down to audio where an audio demodulator
worked, or have an FM receiver so you could use the output of the
discriminator.

With narrow shift, the solution becomes far easier. You can use
just about anything, triangle or even square wave, and feed it into
a low pass filter. Given those traditional frequencies (and they
were chosen to fit into an audio passband but so harmonics would not
be in that passband), the low pass filter can be fixed, and will not
really distort the waveform as the frequency shifts.

People did use square wave tone generators, but of course they
were fed to existing transmitters that would have a response to limit
the audio passband.

Michael
 
Yeah, I've seen a couple since I first posted this question. Most of
the ones I've seen so far don't fit too well in my application. The
best I've seen is the XR2206 and NTE864 (replacement for the ICL8038),
but both appear to operate at 10V+, and I haven't been able to find
low-temp versions (-40C). The MAX038 is 5V and has a low temp version,
but it's hard to find a distributor for that version (and it's a little
pricey). The AD9833 with SPI interface is an option, although I'd
really only be working with 2 output frequencies, so I was hoping to be
able to configure the IC/circuit to modulate between those 2
frequencies with a high or low input.

Thanks again all for all the good options, although I'm still open to
others.

Dave

mike wrote:
dave.harper wrote:

I'm trying to make a radio modem that can be controlled via a PIC.
I've managed to create one that can communicate via RTTY and
AMTOR-FEC
(ham radio protocols) at 100 baud, but the waveform looks like the
PIC
threw up on the oscope. My software is still able to decode it at
100
baud without a problem, but at higher speeds it's becoming an
issue.
So I'm looking for something to create a less nausiating wave form
and
would cause less problems for the recieving software to decode at
higher speeds. That's why I'm concerned with the tolerance on the
frequencies... What about a 555 with tightly toleranced resistors
and
caps, and a double-integrated output...?

Dave


Don't they make single chip modems for this very purpose?
My Baycom has a TCM3105, whatever that is...
mike

--
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Bunch of stuff For Sale and Wanted at the link below.
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Click to expand...
 
On Mon, 31 Jan 2005 14:04:48 +0000, John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Tony Williams
tonyw@ledelec.demon.co.uk> wrote (in
4d35e6c072tonyw@ledelec.demon.co.
uk>) about 'Sine generator IC solution?', on Mon, 31 Jan 2005:
You're not going to do much in the way of a 10:1 tuning range in
Wien bridge- fussy little high Q and amplitude unstable thing
that it is.

The Q of a Wien network is 1/3, not high.
Click to expand...
Wrong ! The effective Q of a Wien bridge varies inversely with the
frequency . A typical Q at 1kHz with a 4 Mhz bandwidth is 400!
 
lemonjuice wrote...
John Woodgate wrote:
Tony Williams wrote...
You're not going to do much in the way of a 10:1 tuning range
in Wien bridge- fussy little high Q and amplitude unstable
thing that it is.

The Q of a Wien network is 1/3, not high.

Wrong! The effective Q of a Wien bridge varies inversely with
the frequency. A typical Q at 1kHz with a 4 Mhz bandwidth is 400!
Click to expand...
... inversely with frequency? Come on folks, let's put the level-
servo loop-gain in there where it belongs. E.g., the "Q" of our
fab AoE 2ppm-distortion Wien-bridge oscillator is well over 400.
Err, "fussy little high Q and amplitude unstable thing" it may be.


--
Thanks,
- Win
 
lemonjuice wrote:
On Mon, 31 Jan 2005 14:04:48 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:

...
The Q of a Wien network is 1/3, not high.


Wrong ! The effective Q of a Wien bridge varies inversely with the
frequency . A typical Q at 1kHz with a 4 Mhz bandwidth is 400!
Click to expand...
Wrong! The Q of a Wien bridge is 1/3 (I'll accept JW's number). The Q
of a Wien bridge _filter_ varies inversely with _feedback_, regardless
of frequency. The Q of a Wien bridge _oscillator_ is (by definition)
_infinite_, regardless of frequency.

jp
 
On Tue, 01 Feb 2005 22:02:43 -0500, John Perry <jp@no.spam> wrote:

lemonjuice wrote:
On Mon, 31 Jan 2005 14:04:48 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:

...
The Q of a Wien network is 1/3, not high.


Wrong ! The effective Q of a Wien bridge varies inversely with the
frequency . A typical Q at 1kHz with a 4 Mhz bandwidth is 400!


Wrong! The Q of a Wien bridge is 1/3 (I'll accept JW's number). The Q
of a Wien bridge _filter_ varies inversely with _feedback_, regardless
of frequency. The Q of a Wien bridge _oscillator_ is (by definition)
_infinite_, regardless of frequency.

jp
Click to expand...
Q = 1/3 implies a lot of phase noise to me. Anybody know for sure?

John
 
In article <2waYaxFAsj$BFwzH@jmwa.demon.co.uk>,
John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Tony Williams
tonyw@ledelec.demon.co.uk> wrote (in <4d35e6c072tonyw@ledelec.demon.co.uk
|
Click to expand...
/|\
More care please John, I didn't write any of the text
you attributed to me.
\|/
|
You're not going to do much in the way of a 10:1 tuning range
in Wien bridge- fussy little high Q and amplitude unstable
thing that it is.
Click to expand...
--
Tony Williams.
 
Yes as I show in my reply below to Larkin
Q wien bridge = GAIN-BANDWIDTH PRODUCT * Q of the frequency selective
network /3 * f
 
Tony Williams wrote:
In article <41FD0BE4.2030700@nospam.com>,
Fred Bloggs <nospam@nospam.com> wrote:


You're not going to do much in the way of a 10:1 tuning range in
Wien bridge- fussy little high Q and amplitude unstable thing
that it is. These days the most practical and high performance
approach, at these frequencies, would be to generate a variable
frequency square wave at fundamental and 100x fundamental which
are then processed by cheap switching tracking filter.


An 8038-variety is still the easiest approach if
not much better than 1% THD is ok.

Your approach is nifty and could be very handy if
(say) something like a 2-phase sine/cosine was required.

Note that there is a 3-step square-wave approximation
of a sine which has zero third harmonic content, very
useful if going into a low pass filter.
Click to expand...
The switched capacitor filters make an application like this virtually
digital- no analog involved, no tuning, no fussing with voltages, a
simple embedded programming application: Digitally Controlled Sine-Wave
Generator-
http://www.maxim-ic.com/appnotes.cfm/appnote_number/2081
 
On Sun, 30 Jan 2005 16:31:35 GMT, Fred Bloggs <nospam@nospam.com>
wrote:

Spehro Pefhany wrote:

An op-amp (or a few discrete transistors if you ignore the "IC
solution" part of the OP's question) and a handful of passives and a
nonlinear element of some kind (lamp, thermistor etc.) can be used to
make a Wien bridge oscillator, probably the most easily adjustable
sine-wave oscillator. But the specs might push the solution somewhere
else. If you google on "Wein bridge" and "Wein bridge" (the latter
has 3 times as many hits, though some may lead you to bridges over the
Danube) you should get some good ideas.


You're not going to do much in the way of a 10:1 tuning range in Wien
bridge- fussy little high Q and amplitude unstable thing that it is.
Click to expand...
Didn't the original HP oscillator do just exactly that?

These days the most practical and high performance approach, at these
frequencies, would be to generate a variable frequency square wave at
fundamental and 100x fundamental which are then processed by cheap
switching tracking filter.
Click to expand...
-----
http://mindspring.com/~benbradley
 
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