Question 4.15: Find the voltage at which the reverse current in a germanium...

We know that the current of a PN junction diode is

$I=I_{0}\left(e^{\frac{V }{V_{T} } }-1 \right)$

Therefore,           $-0.90=I_{0}\left(e^{\frac{V }{V_{T} } }-1 \right)$

where                   $V_{T}=\frac{T}{11.600}=26  mV$

$-0.9=\left(e^{\frac{V}{0.026} }-1 \right)$

$0.1=e^{\frac{V}{0.026}}$

Therefore,            V = – 0.06 V