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Sine Wave Generator.

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vortex2009

New Member


Hi all,

I would like to build a sine-wave generator in the frequency range from 100hz to 600hz, in a battery operated circuit (9 volts), no I have no idea on what chip to use on this.. Im use to the 555 chip and built many weird noises for fun.. some quite anoying!!! anyhow can any of you experts help me please..
& also I would like a volume control so it be low Volume & high like a sweep generator ideally..

I've tried various Google searches.. but to no avail..
thanks
any help at all or a starting point would be great...
much appreciated..
vortex2009
:)
 

Hero999

Banned

audioguru

Well-Known Member
Most Helpful Member
The filters work properly only at a single frequency so it is not a variable frequency sine-wave generator like a Wien Bridge or a Phase-Shift oscillator.
 

Hero999

Banned
Look at the circuit again and read my explanation in the linked post, audioguru.
 
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marcbarker

New Member
Single transistor (or JugFET) Phase shift oscillator? A dual-gang 100 K pot sets the frequency, and the output sinewave is quite pure and stable amplitude over the frequency range.
 

Mikebits

Well-Known Member
I am with Bounty, use the Exar chip.
 

Hero999

Banned
Single transistor (or JugFET) Phase shift oscillator? A dual-gang 100 K pot sets the frequency, and the output sinewave is quite pure and stable amplitude over the frequency range.
Can you build a phase shift with just two variable resistors?

I've never seen one before.

Another suggestion is Wein bridge oscillator.
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
Look at the circuit again and read my explanation in the linked post, audioguru.
Still doesn't really work, it will give a very poor quality sinewave over a limited frequency range, useless for most purposes.

If you really want to make a sinewave oscillator in that kind of way look at analogue synthesisers - use a VCO folowed by a VCF, but it's NOT simple or trivial.

Proper way is a wein bridge, which is easier to make variable over a wide range than a phase shift one.
 

Mikebits

Well-Known Member
Or simply use a chip designed for such a thing. I fail to see why such a simple thing must be overcomplicated. The Exar 2206 works great and is cheap to get.
 

Hero999

Banned
Still doesn't really work, it will give a very poor quality sinewave over a limited frequency range, useless for most purposes.
Have you at least simulated it?
Did you notice the dual ganged pot?

It's probably my fault for not using a pot symbols.

The triangle wave is pretty linear <1%.

The filter's cut-off frequency is over 3× the frequency of oscillation which gives a pretty decent sinewave, probably not as good as a Wein bridge or phase shift but certainly good enough for most applications. It also has the advantage of square and triangle outputs, although this isn't important here.

The THD of the waveform can be reduced further by reducing the amount of hysteresis on the Schmit trigger. Although this will reduce the amplitude of the waveform so will require more gain as well and increase the noise level.

This is the cheapest and crudest way of building a filtered Schmitt trigger oscillator, using a comparator plus dual op-amp might be better.

With the components shown, the frequency range is about 5kHz to 50kHz and the amplitude and quality of the sine wave doesn't change much at either extreme, so 100Hz to 600Hz should be trivial.

There's no reason why this circuit couldn't be used as the basis of a simple function generator, using a dual ganged rotary switch to change the capacitors, from 1nF to 100µF, it should be easy to go from 5Hz to 500kHz.

I'm not saying that this is the best way of doing it, all I'm saying is it shouldn't be ruled out yet.

Here's the circuit again, with the proper pot symbols and simulation results showing the sine wave with it set to about 15kHz.
 

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vortex2009

New Member
Sine wave Generator



Hi all,

I like to say a big thanks for all the replys, It's very appreciated.. I shall do more research myself too!!

dont know if I will succeed..
many thanks again.

vortex2009
:)
 

marcbarker

New Member
Can you build a phase shift with just two variable resistors?

I've never seen one before.
Yes! Very simple too, no need for IC's, split supplies and all that gubbins.



This will output a clean sinewave over range of 50 Hz to 1 kHz.

R* sets the gain of the single-BJT amplifier. It can be 0 Ohm to 47 Ohm. Choose a higher value for low distortion, a lower value for wider frequency coverage.

Of course, it's even better if you use a J-FET and let it self-bias itself to the optimum point. ...'Deja-vous feeling' ... have we've been here before? .... :)

Another suggestion is Wein bridge oscillator.
Another great oscillator!
 
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Hero999

Banned
I understand how it works now, thanks.
 

audioguru

Well-Known Member
Most Helpful Member
A Phase-Shift oscillator uses three]/b] RC networks, not just two.
 

vortex2009

New Member
sine wave gen

Yes! Very simple too, no need for IC's, split supplies and all that gubbins.



This will output a clean sinewave over range of 50 Hz to 1 kHz.

R* sets the gain of the single-BJT amplifier. It can be 0 Ohm to 47 Ohm. Choose a higher value for low distortion, a lower value for wider frequency coverage.

Of course, it's even better if you use a J-FET and let it self-bias itself to the optimum point. ...'Deja-vous feeling' ... have we've been here before? .... :)



Another great oscillator!
Hi there,
thanks for the reply.. I understand bits of the diagram you kindly put up but the dual ganged pot, on how to wire it up? would it be ok if you could dump a vero strip boad of the diagram and the wiring? please.
that circuit looks ideal to me
thanks very much
if you need my email address Just ask ok?
thanks again...
vortex2009
 

Hero999

Banned
A Phase-Shift oscillator uses three]/b] RC networks, not just two.

Have you tried simulating it?

I've tried simulating it with different software packages ant it works.

Attached is the LTSpice version.

Some of the component values need tweaking but it works.

I would recommend making R6 a 200R pot. so you can adjust the gain.

You do need a high gain transistor e.g. BC337-25 or BC547B, it wouldn't work with the 2N2222.
 

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audioguru

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I tried the Phase Shift oscillator and after its output builds up then it clips.
It needs an amplitude regulating circuit to allow it to start faster and stop clipping.
 
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