output offset voltage!

[electronics_kumar]

among all chracteristics for an ideal op-amp,i encountered that output offset voltage is always is always zero...how it is possible

 

[puviarasu]

Do you mean ideal opamp , in that it is the definition.

for practical characteristics of op amp it will be very less or nil as opamps now are very precise.

 

[the_risk_master]

It is due to the CMR of the differential stages
(Ideally offset is zero)

 

[vdaniel]

By definition, the output voltage of an ideal OA is

Vout = g*(V+ - V-)
where g -> eternity

For real OAs, the formula looks like

Vout = g*(V+ - V- + Voffset)

The easiest way to measure Voffset (for unity stable OAs) is to connect the inverting (V-) input to output, and the non-inverting input to GND. The output voltage will be equal to Voffset.

For real OAs, Voffset can be in range from microvolts (for chopper stabilized OAs) to millivolts.

 

[kohtwe]

Hi!

all chracteristics for an ideal op-amp, encountered that output offset voltage is

always zero, it is possible because offset voltage can be noise

but offset voltage (+V/ -V) use op-amp

Goodluck

 

[lavitaebelle]

Offset consists of two parts, systematic offset and random offset. Systematic offset is due to mismatch in device sizing, currents,non symmetry,etc. Random offset is due to device property mismatch such as Vt,effective W,L.
For any opamp designed symmetrically, there will be no systematic offset. Random offset is a statistical parameter, depends on the statistical variation of the device properties.

Of course in an ideal opamp, there is no systematic or random offsets and hence no offset.