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brainbaby

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- TL;DR Summary
- comparing input impedance calculated manually and via ltspice

Hi friends,

Here is a CC amplifier

The objective is to calculate its input impedance.

Two ways are employed.

V1 = 1mV = 0.001 V

V2 = 656.4129mV = 0.6564129 V

R = 1K

Iin = 343.83207µA = 0.0003438 A

Zin = R / V1/V2 -1

Zin = 1001.5257 Ohm (input impedance)

The value on Zin found out by series resistor method is 1001.5257 Ω at 10khz

But Zin calculated

fig- input impedance via Vtest/ Itest (ltspice plot method)

Note: attached are two .asc files which represent the calculation of input impedance using series resistor manual method & plot method i.e Vtest/ I test.

Thanks

Here is a CC amplifier

The objective is to calculate its input impedance.

Two ways are employed.

***calculating input impedance using series resistor method (manual method)**(refer first two attachment)V1 = 1mV = 0.001 V

V2 = 656.4129mV = 0.6564129 V

R = 1K

Iin = 343.83207µA = 0.0003438 A

Zin = R / V1/V2 -1

Zin = 1001.5257 Ohm (input impedance)

The value on Zin found out by series resistor method is 1001.5257 Ω at 10khz

But Zin calculated

**via plot method (ltspice) i.e Vtest/ Itest**is 1909.066 Ω at 10khz for reference**My query is that both the method should yield the same value for Zin.**

Why do the Zin values calculated by both methods differ?Why do the Zin values calculated by both methods differ?

fig- input impedance via Vtest/ Itest (ltspice plot method)

Note: attached are two .asc files which represent the calculation of input impedance using series resistor manual method & plot method i.e Vtest/ I test.

Thanks

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