Question

If you in a lab and you are given a black box, oscilloscope, and function generator. How do you figure out whether the black box is inverting opamp, noninverting opamp, low-pass filter, or high- pass filter? Please tell me the differences. P.S. you can't see the inside of the black box thus you can't tell by looking at the circuit

Answer 1

function generator can be used to apply sinusoidal signal to black box.

Input and output of black box will be observed simultaneously on oscilloscope.

Figure (a), (b) and (c) shows phase relationship between input and output for non inverting and inverting amplifiers.

In case of inverting opamp , there will be 180 degree out of phase relationship between input and output.

Non inverting opamp will have 360 / 0 degree phase difference between input and output.

Figure (d) and (e) shows frequency response of black box if it's a low pass or high pass filter.

Frequency of Input signal from function generator can be varied between few hertz to mega hertz frequency. At output of black box we can observe signal on oscilloscope.

In case of low pass filter, output signal will get attenuated as frequency is increased and hence gain is reduced.

In high pass gain increases as frequency of Input signal is increased.