Sine wave generator

In message , dated Tue, 15 Aug 2006, " snipped-for-privacy@gmail.com" writes

You can do it with one op-amp that has a gain well over 3 at 100 kHz. Google for 'Wien Bridge'. The problem is not getting it to oscillate but controlling the amplitude so you don't get a clipped sine wave. There are many ways of doing it; the best, but costly, is a vacuum thermistor bead. You can use a FET as a voltage-controlled resistor.

It won't do 0 to 100 kHz in one range, though. If you want that (I can't think why), Google for 'Exar function generator'. but it's not as much fun as the Wien bridge solution.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Luhan

In message , dated Tue, 15 Aug 2006, Luhan writes

You don't learn anything much from using one of them. And it costs far more than an op-amp, probably as much as a bead thermistor.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

If you want an "almost all digital" solution, Analog Devices has microcontrollers with built-in DDS generators that will easily meet your specifications. (See:

This is probably serious overkill, however, and certainly not the cheapest solution and nowhere close to the lowest power. The main benefit over, e.g., a wien bridge is that you simply program the output frequency with a digital word, and the result is as accurate as your (e.g., crystal) clock source (if accuracy was unspecified, a crystal is generally considered "far more than accurate enough, with no calibration or drift to worry about...").

A software DDS running on a suitable MCU and DAC should be suitable. An AT90S2313 clocked at 10 MHz should be able to manage 100 kHz.

Leon

** Groper alert !!

** Variable by what means ?

A knob?

A control voltage.

A light beam ?

ESP ???

** Tell us what is the actual problem first.

Or be condemned to hell for eternity as another TROLL.>

....... Phil

Search around for the tiniest incandescent lamp you can find -- if you can find a 6V grain-of-wheat bulb you can use that for the resistive element. I suspect a small thermistor stuck in foam would work almost as well as the vacuum thermistor, and possibly better than the lamp.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

===================================== I recall Mr Hewlitt and Mr Packard made a Very Able sine wave oscillator back in the day... in Palo Alto as I recall....

Yes, the 8038

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

need a bit more info:

variable over what frequency range? Continuously variable? By ranges? Down to 0.001 Hz?

How stable in amplitude and frequency? How good a sine wave? What percent distortion? What output voltage? What kind of load?

In message , dated Tue, 15 Aug 2006, BobG writes

Yes, but amplitude control by incandescent lamp is possible with valves/tubes, but not with normal op-amps.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Wien bridges aren't super easy to control the frequency on. A quad op-amp version of the 3 opamp "state variable" oscillator may be a better option for the OP.

I will even try to ASCII art draw it

R1 /+!---GND ---/\\/\\--+---< ! ! ! \\-!-- ! ! R3 ! ! ---/\\/\\--+ ! R2 ! +--/\\/\\--+---/\\/\\/-- ! ! R4 +---!!---+ ! C1A ! C1B R5A ! ! ---!!--- --/\\/\\-+-!-\\ ! R5B ! ! ! ! >---+----/\\/\\----+-!-\\ ! ! GND--!+/ ! >---+ ! GND-!+/ ! ! ---/\\/\\---+----/\\/\\---------------- ! ! R6 ! R7 ! ! /-!---- --+-< ! \\+!---GND

Normally:

R6 = R7

R1 > 5*R5

R2 = 0.8 * R1

R3 = 1.3 * R4

R5A and R5B can include a POT like this:

---- ! \\ /

In message , dated Wed, 16 Aug 2006, Ken Smith writes

Indeed, it's better but not 'simpel', which was the spec.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

"John Woodgate" a écrit dans le message de news: snipped-for-privacy@jmwa.demon.co.uk...

Never seen an opamp Wien bridge controled by incandescent silicon?

--
Thanks,
Fred.

In message , dated Wed, 16 Aug

2006, Fred Bartoli writes

No, I use a current-limited power supply. For incandescent silicon, you need 1 kW audio amplifiers, or 5 kW lamp dimmers.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

For oscillators my gyrator BP works best... behaves just like a real tank.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Sherman, or Panzer? ;-)

Thanks, Rich

A microcontroller with an 8 bit (R2R) DAC.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

In article , Fred Bartoli wrote: [....]

I work with someone who invented the "light emittng PROM". Way back when EPROMs had a window so you could erase them with UV.

--
--
kensmith@rahul.net   forging knowledge