Question

Given below is a differential amplifier in which V1=V2. What happens to VOIB at this condition?

(a) VOIB= 0

(b) VOIB= VOIB×10^-10

(c) VOIB=  VOIB/2

(d) VOIB= -1

This question was posed to me in unit test.

Query is from Input Bias Current in division Operational Amplifier Fundamentals of Linear Integrated Circuits

Answer 1

The correct answer is:

(a) VOIB = 0

Explanation: In a differential amplifier, if the input voltages V1V_1V1​ and V2V_2V2​ are equal (V1=V2V_1 = V_2V1​=V2​), the differential input voltage is zero. Since the output offset voltage (VOIB) is typically influenced by the difference between the input voltages and the characteristics of the op-amp (including input bias current), if there is no difference between V1V_1V1​ and V2V_2V2​, there is no differential voltage to create an output offset. As a result, the output offset voltage (VOIB) becomes zero in this condition.