Question

Pre-Medical : Physics 225
ALLEN
5.
(a
) Calculate the value of V, andlif the Si diode and the Ge diode start conducting at 0.7 V and 0.3 V respectively
in the given circuit. (b) If the Ge diode connection be reversed. What will be the new values of V, and 1 »
OV
=12 V
52:​

Answer 1

Correct Question :

• Calculate the value of V₀ and l if the Si diode and the Ge diode start conducting at 0.7 V and 0.3 V respectively  in the given circuit. (b) If the Ge diode connection is reversed. What will be the new values of V₀ and I?

Concept :

(a)

Initially, both Ge and Si diodes are connected in forward bias .

The knee voltage of Ge is 0.3V  and that of Si is 0.7 V

Remember when two diodes connected in parallel in forward biaising the diode having the least voltage will conduct electricity [as the voltage across both the diodes will be 0.3 V hence Si will not conduct electricity as it has not crossed it's knee voltage yet]

Hence ,

⇒ V₀ = 12 - 0.3  

⇒ V₀ = 11.7 V

We need the value of the resistor in order to find the value of the current flowing through the circuit.

⇒ I = V₀/ R

⇒ I = 11.7/ R ( As the value of R is not provided to us )

________________________

(b)

Now, the Ge diode is reversed{reverse biasing ] hence no current will flow through it.

Hence,

⇒ V₀ = 12 - 0.7

⇒ V₀ =11.3 V

Now by using ohm's law,

⇒ I = V₀/ R

⇒ I = 11.3/ R