# Obtaining frequency of 550 Hz from Simple Triangle and Square Waveform Generator Circuit

First time asking a question so sorry if I miss some things. I'll try to be thorough and straightforward.

I'm trying to design a square wave from a triangle wave-square wave generator circuit.

The output wave should be running at 550 Hz with a 2 Vpk-pk, and an offset of 1 V, which is why I added a diode network at the output of the second op-amp.

The thing is originally I was having trouble getting the right frequency of the signal. I solved for R1 using the following relationships, setting C1 to 0.1uF:

$$t = R1C1 = \frac{1}{f}$$

Which gave me:

$$R1 = 18.18 k\Omega$$

Also, finding the time using frequency gives me:

$$\tau = 1.82ms$$ My problem is I'm not too sure how R2 and R3 affect the frequency. Basically, I 've been switching out resistor values and found changing R2 affects the frequency the most. 3.42 k, gives me the right tau, but I'm not sure why though.

I know that the second op amp acts as a comparator, right? So I'm guessing the voltage between R3 and R2 is the threshold. But I'm still a little lost on how that relates to the frequency of the signal.

• You may find it more useful to take Waveform A from the output of the 2nd op amp, rather than the point you have chosen. Commented Nov 14, 2020 at 20:44