Question

What will be the output voltage waveform for the circuit, R1×CF=1s and input is a step voltage. Assume that the op-amp is initially nulled.

(a) Triangular function

(b) Unit step function

(c) Ramp function

(d) Square function

This question was addressed to me in my homework.

The doubt is from Integrator topic in division Operational Amplifier Applications of Linear Integrated Circuits

Answer 1

The accurate answer is (c) Ramp function

Simply put: Input voltage Vin = 1.2v for 0≤t≤0.4ms. The output voltage at t=0.4ms is

Vo = (1/R×CF)×^^t∫0 Vindt+C =-(1/1) × ^^0.4∫01.2 dt

=> Vo =-[^^0.1∫01.2 dt + ^^0.2∫0.11.2 dt + ^^0.3∫0.21.2 dt + ^^0.4∫0.31.2 dt ] = -(1.2+1.2+1.2+1.2) = -4.8v

Therefore, the output voltage waveform is a ramp function.