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.

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.

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

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

A knob?

A control voltage.

A light beam ?

ESP ???

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.

===================================== 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

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.

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.

"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?

In message , dated Wed, 16 Aug

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

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 | |

Sherman, or Panzer? ;-)

Thanks, Rich

A microcontroller with an 8 bit (R2R) DAC.

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.