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A function generator base on LM324

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Junker_eu

New Member
As attached circuit,this is a triangle wave form generator.Do you know how the circuit working and generate the wave form?And how to calculate the frequency of it?Please tell me some theory of it.
 
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audioguru

Well-Known Member
Most Helpful Member
The circuit is not a "normal" triangle/square-wave generator. It is more complicated and might not work.

The lousy old LM324 quad opamp works only at low frequencies.

This is a normal circuit:
 

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kchriste

New Member
Forum Supporter
Junker_eu, your circuit looks like it has errors. Try a circuit like this instead.
EDIT: I see AG has already replied.
 
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Junker_eu

New Member
There is no doubt that it works and generate a smooth triangle wave of ~40HZ.It has used in one of my projects.
 
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kchriste

New Member
Forum Supporter
It looks like you are using the current limiting function of U1-B to charge/discharge the two 22uF caps at a set rate. Unconventional to say the least. What kind of a waveform do you get on pin 7 of the LM324?
 

Roff

Well-Known Member
I simulated it. It oscillates, but it is not a function generator. Use the circuit that kchriste linked to.
 

Junker_eu

New Member
Hi,Roff

May be I don't know what can be called a function generate.But that isn't important for me.As you simulate,it oscillate,can you tell me how can it oscillate and how to change the frequency of it?
 
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Roff

Well-Known Member
Hi,Roff

May be I don't know what can be called a function generate.But that isn't important for me.As you simulate,it oscillate,can you tell me how can it oscillate and how to change the frequency of it?
Why can't you use the circuit kchriste linked to? I don't want to waste my time fooling with a junk circuit.
 

Roff

Well-Known Member
You say the circuit is a junk because that you don't understand it at all.
You're right. I don't understand it. I know that you don't understand it either. I doubt that anyone here does. It obviously wasn't designed by a competent circuit designer. Why don't you use a circuit that provides predictable results, and better waveforms?
 

kchriste

New Member
Forum Supporter
It is "junk" because it's behavior is undefined. ie: It won't work the same with different OpAmps.
It also uses more parts than the circuits that AudioGuru and I posted.

AG's circuit uses 3 resistors, one capacitor and two OpAmp sections.
Your circuit uses 5 resistors, 4 capacitors, a diode and two OpAmp sections for a total of 6 additional components.
 
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