Question 4.17: Find the value of dc resistance and ac resistance of a germa...

Given                              I_{o} = 25 μA, T = 25°C = 298 K and V = 0.2 Volts

I=I_{o}\left(\frac{V}{e^{\eta V_{T} } }-1 \right) =25\times 10^{-6}\left(\frac{0.2}{e^{26\times 10^{-3} } }-1 \right) =54.79mA

d.c. resistance                R_{F}=\frac{V}{I}=\frac{0.2}{54.79\times 10^{-3} }=3.65\Omega

For germanium,            \eta =1, V_{T}=\frac{KT}{q}=25.71mV

a.c. resistance                 r_{F} =\frac{\eta V_{T}}{I} =\frac{25.71\times 10^{-3} }{54.79\times 10^{-3}} =0.47\Omega