1. The abbreviation PIV in the case of a diode stands for
a) Peak Inferior Voltage
b) Problematic Inverse Voltage
c) Peak Inverse Voltage
d) Peak Internal Voltage
Answer: c [Reason:] PIV stands for Peak Inverse Voltage. It is the maximum reverse bias voltage which a diode can bear without breakdown.
2. What is mean by PIV rating of a diode
a) Maximum reverse bias potential which can be applied across a diode without breakdown
b) Maximum forward bias potential which can be applied across a diode without breakdown
c) Minimum potential required by a diode to reach conduction state
d) Maximum power allowable to a diode
Answer: a [Reason:] PIV rating indicate the maximum allowable reverse bias voltage which can be safely applied to a diode. If reverse potential is greater than PIV rating then the diode will enter reverse breakdown region.
3. The voltage after which the diode current exponentially increases with forward bias is NOT known as
a) Offset voltage
b) Threshold potential
c) Firing potential
d) Peak forward voltage
Answer: d [Reason:] The voltage after which a diode increases rapidly is known as offset voltage, threshold voltage, firing potential and cut-in voltage. Beyond this voltage the forward bias voltage overcomes the potential barrier and rapid conduction occurs.
4. The diode current equation is not applicable in
a) Forward biased sate
b) Reverse biased state
c) Unbiased state
d) It is applicable in all bias sates
Answer: d [Reason:] Diode equation is I=I0 (e(qV/kT)-1). It is applicable in all bias condition that is forward, reverse and unbiased states.
5. Emission coefficient of Germanium is
Answer: a [Reason:] Emission coefficient or ideality factor accounts the effect of recombination taking place in the depletion region. The range of factor is from 1 to 2.For Germanium it is 1.
6. The ideality factor of Silicon is
Answer: b [Reason:] Emission coefficient or ideality factor accounts the effect of recombination taking place in the depletion region. The range of factor is from 1 to 2.For silicon it is 2.
7. The value of voltage equivalent of temperature at room temperature(27oC)
Answer: a [Reason:] Voltage equivalent of temperature VT is equal to the product of boltzman constant and temperature. At room temperature it is 26mV.
8. What happens to cut-in voltage when temperature increases?
a) Cut-in voltage increases
b) Cut-in voltage decreases
d) Cut-in voltage either increases or decreases
e) Cut-in voltage doesn’t depend on temperature
Answer: b [Reason:] As temperature increases conductivity of a semiconductor increases. The diode conducts smaller voltage at larger temperature. Therefore, cut-in voltage decreases.
9. When temperature increases reverse saturation current
c) Doesn’t depend on temperature
d) Either increases or decreases
Answer: a [Reason:] As temperature increases conductivity of a semiconductor increases. Reverse saturation current increases as temperature increases.