Triangular and sinusoidal signal generator project

Thread Starter

Iulia Baginean

Joined Apr 22, 2017
3
Hi! I need a little help with my school project.
I have to simulate in Pspice a triangular and sinusoidal signal generator with adjustable frequency and amplitude. I tought about using an astable multivibrator to generate a rectangular signal, which output goes into an integrator circuit to obtain a triangular waveform and after integrating this one I should get a sinusoidal wave.
The problem is that after simulating I don't get any of the waveforms I want. I tried to simulate each part. From the astable multivibrator I get a trapezoidal signal instead of a rectangular.
Can you help me a little bit? Maybe it's the idea bad from the begining
Thanks
 

AlbertHall

Joined Jun 4, 2014
9,876
The '741 is old and has very limited rise time and gain bandwidth product. Either try a much lower frequency or a faster opamp.
 

AnalogKid

Joined Aug 1, 2013
8,465
First, you can't get a 10 kHz squarewave out of a 741. It does not have sufficient gain-bandwidth. Of course, your simulation program might not know this, depending on the quality of it's 741 model.
Second, unless the components are perfectly matched, the integrator will not make a perfect triangle wave because its timing has to be exactly the same as the square wave. If its time constant is a bit smaller, the triangle wave will be clipped. If its timing is a bit larger, the triangle will diminish to zero.

Search the web for function generator circuits, and you will see many examples of making the first opamp a comparator. Its output still will be a squarewave, but it will self-align to the timing parameters of the integrator for a constant integrator output amplitude regardless of frequency.

ak
 
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