Question

When input is positive, then output is?

(a) growing exponential signal

(b) decaying exponential signal

(c) positive going ramp

(d) negative going ramp

The question was posed to me in an interview.

The origin of the question is Voltage to Frequency Converter Type Integrating DVM topic in chapter Electronic Instruments of Electrical Measurements

Answer 1

Right option is (d) negative going ramp

To explain I would say: The op amp produces a negative going ramp signal for a positive input voltage. Capacitor is discharged after some time and the output returns to zero. The next cycle starts and the output is a sawtooth waveform. Figure shows the output sawtooth waveform.