This topic is taught in ELEC2133 and ELEC3106.
Input Offset Voltage refers to the voltage which needs to be applied to the input terminals of an Op-Amp to produce an output of zero volts.
You must have a knowledge of the function and rules of Op-Amps to fully understand this topic. This can be gained from ELEC2134 Circuits and Signals or ELEC2133 Analogue Electronics.
Input Offset VoltageEdit
Input Offset Voltage refers to the voltage required at the input terminals of an Operational Amplifier to make the output voltage zero. It can be found by:
- Tweaking the input voltage until the output voltage settles to zero, or
- Setting the input voltage to zero and measuring the output voltage.
If you use the second method, you must then divide by the closed-loop gain of the amplifier.
Countering the Input Offset VoltageEdit
In DC situations, the Input Offset Voltage can be nulled by introducing a small voltage source in series with one of the input terminals, so that a zero volt signal applied to the inputs will actually apply the correct offset voltage required to bring the output to zero.
In AC situations, the best solution is to change the feedback to AC coupling, effectively reducing the DC gain to unity.
The Circuit Designer's Companion - Tim Williams
Operational Amplifiers - Coming soon!