I have built an active band-pass filter on a breadboard with the use of an MC33078p op amp. Gain is 32 on paper.
When I apply the AC signal to the circuit, 18.1mV P-P and 660kHz, the oscilloscope measures a voltage of 1.22V at the output but with zero frequency. When the earth probe is not connected, I measure a frequency of between 30 and 60 Hz.
Is there any obvious reason for this?
As well as the frequency problem, the output voltage doesn’t seem to be inverted, it’s a fairly basic circuit and don’t believe I’ve connected anything wrong.