LvW said:The most direct, simple and precise way to simulate the opamp offset voltage is based on its definition:
Offset Voltage Vo is the voltage to be applied between both opamp terminals to bring the output to ZERO (assuming dual supply voltages).
Simulation steps:
1.) Connect a dc source VDC to the non-inv. terminal and ground the inv. terminal.
2.) Perform a dc sweep and display Vout.
3.) What you see is the opamp transfer characteristic (which for an offset free opamp should cross the point 0/0)
4.) The curve crosses the x-axis (VDC axis) at Vo.
5.) That means you have to apply a voltage Vo at the non-inv. terminal to bring the output to zero. That is per definition the offset voltage. Thats all.
Addendum: The dc sweep should be between -5mV and +5mV with a resolution of 1 mikroVolt
supreet_95 said:For knowing the offset voltage error, u acn connect the offamp is unity gain topology and apply a voltage sweep (of low freq or do DC sim over ur input range). Then substraction of input and output waveforms gives u the offset value for the whole input range. This offset will have 3 components:- linear (gain), constant (DC) and non linear, last one being the problematic.
Hope this helps.
LvW said:Don´t worry about rail-to rail. This has nothing to do with offset !
Look at the definition of Vo !
contribution of supreet_95: Confusing ! Offset voltage is specified as cited by me. That´s all. Vo is one specific value given in each data sheet together with an uncertainty range (minimum, nomnal, maximum)
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