Consider avalanche breakdown in a silicon p+n junction. The n-region is uniformly doped with a donor density ND. Assume that breakdown occurs when the magnitude of the electric field at any point in the device becomes equal to the critical field Ecrit. Assume Ecrit to be independent of ND. If the built-in voltage of the p+n junction is much smaller than the breakdown voltage, VBR, the relationship between VBR and ND is given by
A. $${{\text{V}}_{{\text{BR}}}} \times \sqrt {{{\text{N}}_{\text{D}}}} = {\text{constant}}$$
B. $${{\text{N}}_{\text{D}}} \times \sqrt {{{\text{V}}_{{\text{BR}}}}} = {\text{constant}}$$
C. $${{\text{N}}_{\text{D}}} \times {{\text{V}}_{{\text{BR}}}} = {\text{constant}}$$
D. $$\frac{{\sqrt {{{\text{N}}_{\text{D}}}} }}{{{{\text{V}}_{{\text{BR}}}}}} = {\text{constant}}$$
Answer: Option C
The forbidden energy gap between the valence band and conduction band will be least in case of
A. Metals
B. Semiconductors
C. Insulators
D. All of the above
For a NPN bipolar transistor, what is the main stream of current in the base region?
A. Drift of holes
B. Diffusion of holes
C. Drift of electrons
D. Diffusion of electrons
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
For a P-N diode, the number of minority carriers crossing the junction depends on
A. Forward bias voltage
B. Potential barrier
C. Rate of thermal generation of electron hole pairs
D. None of the above

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