Question

The error voltage in a compensating inverting amplifier is obtained by

(a) Multiplying △T to total output offset voltage

(b) Multiplying △T to input offset voltage

(c) Multiplying △T to input offset current

(d) All of the mentioned

This question was posed to me during an online exam.

The above asked question is from Thermal Drift in portion Operational Amplifier Fundamentals of Linear Integrated Circuits

Answer 1

The correct answer is:

(b) Multiplying △T to input offset voltage

Explanation:

In the context of thermal drift in operational amplifiers, the error voltage is primarily related to changes in the input offset voltage due to temperature variations. The input offset voltage (VioV_{io}Vio​) is known to exhibit a thermal drift, meaning it changes with temperature, typically expressed as a temperature coefficient (e.g., mV/°C).

When the temperature changes by △T (the temperature change), the input offset voltage will also change, resulting in an additional error in the output. The error voltage due to thermal drift can be calculated by multiplying the input offset voltage by the temperature change ($△T$).

Thus, the formula for error voltage due to thermal drift is often:

$$\text{Error Voltage}=\Delta T\times \text{Input Offset Voltage}$$

This accounts for the temperature dependence of the input offset voltage. Other parameters like input offset current and output offset voltage are related but do not directly contribute to the error in this specific context of thermal drift.