another sinewave oscillator question

K

kyussinchains

New Member
I'm trying to design a sinewave oscillator with easily adjustable frequency output (from 10-120kHz) I've been playing with a variety of wein bridge type doodads, but my main problem is that I'm trying to mount this thing in a box and want to control the frequency with a single pot, rather than a multitude of resistances which must all be set to the same value....

anyone want to share any great (relatively simple if possible) circuit ideas?
 
DDS (Direct digital Synthesis) would work.

Maybe overkill, it would need a processor and some way to get the processor to read the pot, but it gives a sinewave output with no resistors to adjust.
 
Micro controllers can do DDS, I'm not sure what resolution you'd get at 120khz though.
 
For the DDS, you can use an adjustable frequency oscillator feeding a counter feeding an EPROM (loaded with sinewave table) feeding a DAC. Should be able to get pretty good results, but it's a lot of work.

Or just use a ready made function/waveform generator IC (there are quite a few around), such as the MAX038 (up to 20MHz output, sin/square/triangle w/ adjustable frequency & duty cycle).
 
Unfortunately the output is squarewave, not sinewave.
 
XR2206 goes to 1MHz and is in active production:
**broken link removed**
 
thanks for the responses guys, TBH I'd like to avoid DDS if possible, currently I'm using a max038 which I've had for a while, but it's on a seperate pcb and I'm trying to integrate everything onto a single large board, so unfortunately it needs replacing, the XR2206 looks interesting, although it appears that it's in production in australia which makes getting hold of one a costly and time consuming affair.... I'll see if I can get hold of one to try it out
 
You can always ask the manufacturer for a sample.
 
The XR2206 is a fairly common device which has been in production for a long time. Many hobbyst type distributors will stock it.

I have used it in the past, and it is fairly simple to use. If you have access to a THD meter, you can trim out the THD to 1% or better levels easily.
 
I am going to construct an ultrasonic listener based on a schematic from a magazine. The designer/author used an LM567 as a source (I presume sine wave). I looked at the datasheet and shows an audio oscillator as a normal application - adjusted via pot. I do not know the range.
 
The LM567 doesn't produce a sinewave.

Here's an idea I had for a function generator.

Pot1A/B is a dual ganged pot.

As long as C1 = C2 and Pot1A = Pot1B then the amplitude won't change much but the frequency will.

A to F are CMOS logic gates.

A and B from a Schmitt trigger.

C is a logic inverter.

A to C from a Schmitt trigger oscillator.

D to F are all configured as linear amplifiers.

C2 filters the amplified triangle wave, converting it into a sinewave.

This circuit should have no problems working at 120kHz but you'll need to change the component values - it's probably better to simulate it than to do all the calculations.

The same circuit could be made using a comparator, plus a couple of op-amps for the buffers.
 

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