The built in potential of a p-n junction is 0.8 V. The depletion
| The built in potential of a p-n junction is 0.8 V. The depletion capacitances of the junction at a forward bias of 0.7 V and reverse bias if 0.8 V are C0.7f and C0.8r respectively. The Ratio of C0.7f / C0.8r is _____ [Assume step graded junction]
A. 4
B. ¼
C. 16
D. 1/16
Please scroll down to see the correct answer and solution guide.
Right Answer is: A
SOLUTION
Concept:
The junction capacitance Varies
\({C_j} \propto \frac{1}{{{{\left( {{V_o} - V} \right)}^{\frac{1}{2}}}}}\)
V = applied voltage
Calculation:
Vo = 0.8 V
At forward bias of 0.7 V
\({C_{o.7f}} \propto \frac{1}{{{{\left( {0.8 + 0.8} \right)}^{\frac{1}{2}}}}}\)
\(\frac{{{C_{0.7f}}}}{{{C_{0.8r}}}} = \frac{{{{\left( {1.6} \right)}^{\frac{1}{2}}}}}{{{{\left( {0.1} \right)}^{\frac{1}{2}}}}} = \sqrt {\frac{{16}}{1}} = 4\)