Question

Each diode in the circuit has \(10\Omega\) resistance in forward bias and infinite resistance in reverse bias. Find the time constant of the circuit. Given: \(R=100\Omega\), \(C=0.2\,\mu F\).

• A. \(20\,\mu s\)
• B. \(22\,\mu s\)
• C. \(18\,\mu s\)
• D. \(5\,\mu s\)

Answer 1

The Correct Option is B

Concept:
The time constant of an RC circuit is \[ \tau = RC \] where \(R\) is the effective resistance in the circuit and \(C\) is the capacitance. Step 1: Determine effective resistance. The circuit contains a resistor \(R=100\Omega\) and a diode. Only one diode conducts in forward bias, contributing a resistance of \(10\Omega\). Thus, \[ R_{eq}=100+10=110\Omega \] Step 2: Calculate the time constant. \[ \tau = RC \] \[ \tau = 110 \times 0.2\times10^{-6} \] \[ \tau = 22\times10^{-6}\,s \] \[ \tau = 22\,\mu s \]