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[edit] The ideal op-amp
For any input voltages the ideal op-amp has infinite open-loop gain, infinite bandwidth, infinite input impedances resulting in zero input currents, infinite slew rate, zero output impedance and zero noise.
Asuming you are talking about an ideal op-amp.
There is no current flowing into the terminal.
This is like a open circuit connection.
Open circuit connect have infinite impedance.
Practical op-amp have leakage.
Very little current do flow into the terminal.
Althrough impedance is not infinite,
impedance is still consider large at the terminal.
An opamp uses differential amplifier at the input stage. and the inverting and noninverting terminals are nothing but the two base terminals of the differential pair. now for an ideal opamp it is considered that the bjts of the diff amp are ideal so same current drawn by both, hence the net current flow to the opamp is zero.
therefore it is considered that the i/p impedance is infinite.
in practical case this is not true, and i/p impedance varies from 10Λ5 Ω onwards.
hi
the input impedance of opamp is ideally infinite but not practically.ideally becoz our basic assumption is the two sides of the diff.amp is symetric which is the first stage of opamp.
For ideal opamp the input impedance in infinite so no current passes through the input terminals. actually the first stage of the opamp is an differential amplifier .
HI
if u check the input impedance using multimeter at the input terminals it will show u the value in some mega ohms. It means it does not draw any current for it operation.
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