Op-amp input imperfections: The small DC voltage that must be applied between the inputs of an op-amp to force the differential output to zero is called what?

Introduction / Context:Real operational amplifiers exhibit non-ideal input characteristics. Even with both inputs shorted together, the output may not be exactly zero due to internal transistor mismatches. A small compensating DC voltage is often required to null this error, and it has a standard name in op-amp specifications.

Given Data / Assumptions:

• Linear operation around zero output.
• Common definitions from op-amp datasheets.
• Neglecting temperature drift and long-term aging for this definition.

Concept / Approach:The term “input-offset voltage” denotes the small differential DC voltage that must be applied between the + and − inputs to drive the output to exactly zero. Typical values range from microvolts to millivolts depending on op-amp type. This is distinct from input bias current (the DC current flowing into the inputs) and from slew rate (a large-signal dynamic parameter).

Step-by-Step Solution:

Verification / Alternative check:Datasheets specify V_os (input-offset voltage) and sometimes provide test circuits and typical distributions. Applying ±V_os/2 to opposite inputs cancels the inherent offset and centers the output.

Why Other Options Are Wrong:Input-offset current: difference between bias currents at the two inputs, measured in amperes, not volts. Input bias current: average DC current into each input pin. Slew rate voltage: not a standard term; slew rate is dV/dt capability, not a static offset.

Common Pitfalls:Confusing offset voltage with drift (temperature dependence) or noise; mixing units (volts vs amperes).

Final Answer:input-offset voltage