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

a) The forward voltage is 0.23 V

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

Step-by-step 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^{(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^{(v_(f) )/(0.025) }-1)`

`10000I_(s) = I_(s)(e^{(v_(f) )/(0.025) }-1)`

Dividing through by Is,

`10000 = (e^{(v_(f) )/(0.025) }-1)`

`10000 +1= e^{(v_(f) )/(0.025) }`

`10001= e^{(v_(f) )/(0.025) }`

Taking the natural logarithm of both sides,

`ln(10001)= {(v_(f) )/(0.025) }`

`9.21= {(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^{(v_(f) )/(0.025) }-1)`

`I_(d) = I_(s)(e^{(0.7)/(0.025) }-1)`

`I_(d) = I_(s)(1.45*10^(12) -1)`

`I_(d) = (1.45*10^(12)I_(s))A`