Question

The formula for output offset voltage of an op-amp due to input bias current

(a) VOIB= RF*IB

(b) VOIB= (RF+R1)/IB

(c) VOIB= (1+RF)*IB

(d) VOIB= [1+(RF/R1)]*IB

I had been asked this question by my school teacher while I was bunking the class.

The above asked question is from Input Bias Current in chapter Operational Amplifier Fundamentals of Linear Integrated Circuits

Answer 1

The formula for the output offset voltage of an op-amp due to input bias current is:

VOIB=(1+RFR1)×IBV_{OIB} = \left(1 + \frac{R_F}{R_1}\right) \times I_BVOIB​=(1+R1​RF​​)×IB​

This formula accounts for the contribution of the input bias current IBI_BIB​, the feedback resistor RFR_FRF​, and the resistor R1R_1R1​ connected to the non-inverting terminal.

Correct Answer:

(d) VOIB = [1 + (RF/R1)] * IB