# input impedance

#### raghuveer

Joined Jun 4, 2008
7
HI

I want to calculate the i/p impedance of my circuit(which is having so many passive and active components).Can anybody tell me how to calculate the input and output impedance?Is there any device which calculates these resistances?

Assume any circuit which should have active component(opamp) and passive components?

Plz reply urgent ........i will be waiting ...

#### mik3

Joined Feb 4, 2008
4,843
HI

I want to calculate the i/p impedance of my circuit(which is having so many passive and active components).Can anybody tell me how to calculate the input and output impedance?Is there any device which calculates these resistances?

Assume any circuit which should have active component(opamp) and passive components?

Plz reply urgent ........i will be waiting ...
Your input impedance is not constant if the frequency of your signal changes. Apply a series of sine waves with different frequencies but fixed amplitude and measure the current into the circuit. Then divide the sine's wave voltage by the corresponding current for each frequency to find the impedance at this frequency. Finally, make a graph of impedance vs frequency to see how it varies.

#### hgmjr

Joined Jan 28, 2005
9,029
To assist you in this endeavour, we will need a diagram/schematic of the circuit configuration in whose input and output impedance you are interested.

Can you post one for us to examine?

hgmjr

#### roddefig

Joined Apr 29, 2008
149
A network analyzer is the usual tool to measure the network parameters (impedance) of a circuit over a range of frequencies. They tend to be rather expensive, but if you have access to one it would be the most straight-forward and accurate way to measure the impedance of your circuit.

#### bloguetronica

Joined Apr 27, 2007
1,372
We can't help you without a circuit diagram with the components specified. Please, can you post a diagram? We simply cannot guess.