Analysis :-  Input Impedance
To measure the input impedance of an amplifier, filter or oscillator using circuit maker, use the signal generator
but set the amplitude to a current of 1 amp. Set up your circuit as below:

Perform an ac analysis in the frequency spectrum at the frequencies of interest, measure at point B , the y-axis
will then become the input impedance of your circuit. See example below:

The cursors allow easier reading intermediate points. The input impedance rises at dc as the 1u input coupling
capacitor series impedance reaches  maximum value.  The 100M shunt resistor across the genetator is
necessary as the output impedance of a current source in circuit maker is infinite, omitting this will result in a
simulation error.

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