Op-Amp: Input Offset Voltage Explained
In this video, Input offset voltage in op-amp has been explained.
This input offset voltage is one of the DC offsets in op-amp.
DC offset is the unwanted DC output voltage which appears at the output of the op-amp in addition to the desired signal.
In this video, you will understand what is input offset voltage, how it can affect the output of the op-amp and how the effect of this input offset voltage on the output can be reduced.
What is input offset voltage?
Input offset voltage is the differential voltage which is required to apply between the two terminals of the op-amp such that the output of the op-amp will become zero when no input is applied to the op-amp.
It is hard to predict the polarity of this input offset voltage and usually, in datasheets, the absolute value of input offset voltage is defined.
This input offset voltage ranges from few mV (for general purpose op-amps) to less than 1uV (for high precision chopper stabilized op-amps)
Cause of input offset voltage:
Input offset voltage arises because of the mismatch between the two transistors of the differential amplifier in the op-amp.
Ideally, both transistors should be identical when they are made on the same wafer, but because of some mismatch, these transistors have different biasing points.
This difference in voltage used to get amplified by the other internal stages of the op-amp and it appears as DC offset at the output of the op-amp.
Effect of input offset voltage on feedback circuit:
Whenever op-amp is used in the feedback configuration, then this input offset voltage used to get multiplied by the DC gain of the feedback configuration. And output offset voltage is the multiplication of DC gain and the input offset voltage.
How to remove the effect of input offset voltage on output:
The effect of input offset voltage on the output can be nullified by using the nulling /compensation circuit or it can be reduced by using the very high precision chopper stabilized op-amps, which has very low input offset voltage.
Offset voltage drift:
This input offset voltage also changes with temperature and in datasheets, it used to defined in units of uV/C.
Timestamps for the different topics covered in the video:
1:00 What is input offset voltage?
3:27 Effect of input offset voltage on the feedback circuits
7:08 Offset voltage drift with temperature
7:56 Example
This video will be helpful to all students of science and engineering in understanding the input offset voltage in op-amp.
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