Op-amps
Op-amps
(OP)
How would I calculate offset on the output of an inverting amplifier due to the bias current specification of the circuit, for a particular amplification factor?
Thanks for the help.
Thanks for the help.
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RE: Op-amps
Example.
An inverting amplifier with 100 kohms to inverting input and 1000 kohs feedback. 100 kohms from noninverting to ground. Bias current out of both inputs is 1 microampere (high value chosen for clarity).
Non-inverting will be at 1x100//1000 = 91 millivolts and non-inverting will be at 1x100 = 100 mV. The difference is 9 mV and that is also your offset. You may also need to add the voltage offset.
Gunnar Englund
www.gke.org
RE: Op-amps
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com - kcress@<solve this puzzle>
RE: Op-amps
Gunnar Englund
www.gke.org
RE: Op-amps
Note that these "virtual input offset voltages" are not measurable directly. The bias current created offset voltage due to the non-inverting input will appear on the non-inverting input to the opamp. You will be able to measure it with a DVM. The inverting input will not show a voltage error due to the bias current in the inverting input.