Question

At what forward voltage does a diode conduct a current equal to 10,000 Is ? In terms of Is , what current flows in the same diode when its forward voltage is 0.7 V?

Answer 1

Answer:

a) The forward voltage is 0.23 V

b) The current that flows  $I_{d} = (1.45*10^{12}I_{s})A$

Explanation:

The forward voltage is the minimum voltage that must be applied to a diode before it starts to conduct. The equation is given by:

a) At what forward voltage does a diode conduct a current equal to 10,000 Is ? In terms of Is

$I_{d} = I_{s}(e^{\frac{v_{f} }{0.025} }-1)$

Where:

Id is the diode current = 10000Is,

Vd is the forward voltage at which the diode begins to conduct,

Is is the saturation current.

$I_{d} = I_{s}(e^{\frac{v_{f} }{0.025} }-1)$

$10000I_{s} = I_{s}(e^{\frac{v_{f} }{0.025} }-1)$

Dividing through by Is,

$10000 = (e^{\frac{v_{f} }{0.025} }-1)$

$10000 +1= e^{\frac{v_{f} }{0.025} }$

$10001= e^{\frac{v_{f} }{0.025} }$

Taking the natural logarithm of both sides,

$ln(10001)= {\frac{v_{f} }{0.025} }$

$9.21= {\frac{v_{f} }{0.025} }$

multiplying through by 0.025

${v_{f} }= 0.23$ = 0.23 V

The forward voltage does a diode conduct a current equal to 10,000 Is is 0.23 V

b) what current flows in the same diode when its forward voltage is 0.7 V?

$I_{d} = I_{s}(e^{\frac{v_{f} }{0.025} }-1)$

$I_{d} = I_{s}(e^{\frac{0.7}{0.025} }-1)$

$I_{d} = I_{s}(1.45*10^{12} -1)$

$I_{d} = (1.45*10^{12}I_{s})A$