Accompanying slides to my video blog. What is opamp offset voltage? How to measure it? See video: https://www.youtube.com/watch?v=DVYpzmfQ_r4 See my video blog: https://www.youtube.com/channel/UCtUcgFWvhZbknS5LxvfbMrw

1. #4 Opamp Offset voltage
Exploring the intrinsic properties of operational
amplifiers

2. What is opamp offset voltage?
Opamps are imperfect devices
Many properties define the performance
Input Offset voltage defines the voltage deviation from actual Voltage input
This can be seen as an intrinsic error source either by design or by fault
It is a major factor influencing accuracy and price
The error is usually found to be in the range of a few mV down to a few uV
Examples:
LM358 is a cheap and low power Opamp with a reasonable offset of about 2mV

3. What is opamp offset voltage? #2
Opamp ICs with more than one opamp element will
differ per opamp element
Some Datasheets show deviation frequency over a
large sample range (the cheap LM358 datasheet
does not illustrate this property)
However we can measure this offset with a simple
Circuit and a Multimeter with a mV range

4. Opamp Offset voltage measurement circuit
Opamp in voltage follower/Buffer mode
Bias the Non-inverting input to the middle of
the Supply Voltage (as depicted)
Measure the output with DMM (mV DC)
between the output and the Bias Voltage
(as depicted)
Good quality Multimeter is key, as
measurements would be very small
Ensure Supply (Vcc) Voltage well within the
operating range of the Opamp (LM358

5. Circuit on breadboard
mV
mV

6. Photo of circuit on [mini] breadboard

7. Testing Opamp Offset voltage (LM358)
Channel 1 - Offset Voltage: 0.57mV

8. Testing Opamp Offset voltage (LM358)
Channel 2 - Offset voltage: 0.94mV

9. Conclusion
LM358 Channel 1: 0.57mV
LM358 Channel 2: 0.94mV
This is well within the specified rating of 2mV in the Datasheet
Price
LM358: $0.44 (Digikey)
When interfacing with an ADC and an MCU, it is possible calibrate the offset out
in software
Some Opamps include an offset nulling adjust pin to calibrate in hardware