Hi guys

I am building a function generator based around the above I.C, I have got a wonderfully clean square wave but when I vary the voltage on pin 3 to adjust the amplitude, nothing happens.

just for test purposes I have a pot one end on 12V, one end on 0V and the wiper going direct to pin 3 of the device, the voltage on pin 3 varies as I would expect on pin 3, but the output of my square wave stays constant, I am wondering if I might have a faulty chip?

Neil.

 

It might help if you provided us with the complete circuit diagram.

 

Hello,

You are not supposed to connect a potmeter between 0 and +12 Volts on pin 3.

The pin 3 is for adjusting the output voltage of the sinewave and triangle.
It will do nothing on the squarewave.

Bertus

 

I am just configuring it that way for test purposes Bertus.

ok I will experiment with the other waveforms and see what happens.

thanks

Neil.

 

ok just checked things out and yes the sinewave output (pin2) responds nicely to voltage applied at pin 3, BUT.....the peak to peak of the sinewave itself doesn't adjust, only the D.C level on which it sits varies?

Neil.

 

So how can I get the bottom of the sinewave to sit at 0V? if I add a cap in series with the output the sinewave straddles the 0V rail. being equally above and below......or is this how it is supposed to be?

 

If you put a cap in series that is called a DC blocking capacitor, i.e. it blocks the DC.

In other words it makes the average voltage zero.

That is what a DC blocking capacitor is supposed to do. It would make a perfect sine wave straddle 0V.

 

Great, it's all working then, thanks everyone for your help.

Neil.