Consider a circuit consisting of a capacitor (20 μF), resistor (100 Ω) and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is 10 Ω. The time constant of the circuit is 10-3 s. The value of is . [figure]
- 2.2
- 2.0
- 2.1
- 2.4
Answer
(1) 2.2
Solution
[figure]
The two diodes are connected in parallel with opposite polarities: for any direction of current one diode is forward biased (10 Ω) and the other is reverse biased (non-conducting).
⇒ The diode pair acts as a single 10 Ω resistance in series with R.
Total resistance: Req=100+10=110
Time constant: =ReqC=110 20 10-6=2.2 10-3 s
∴ =2.2
Answer: (1)