1. What is quiescent point or Q-point?

a) Operating point of device

b) The point at which device have maximum functionality

c) The point at which current equal to voltage

d) The point of V-I graph where slope is 0.5

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Answer: a [Reason:] Quiescent point of a device represents operating point of a device. For a diode quiescent point is determined by constant DC current through the diode.

2. The reciprocal of slope of current-voltage curve at Q-point gives

a) AC resistance

b) Nominal resistance

c) Maximum dynamic resistance

d) Minimum impedance

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Answer: a [Reason:] Reciprocal of slope of I-V graph at q-point gives AC or dynamic resistance. The inverse of slope will be change in voltage by change in current which is known as dynamic resistance.

3. As slope of I-V graph at Q-point increase ac resistance will

a) Increase

b) Decrease

c) Either increase or decrease

d) Neither increase nor decrease

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Answer: b [Reason:] Slope of I-V graph at q-point is reciprocal of dynamic or AC resistance. Therefore, as slope increases resistance decreases.

4. Static resistance of a diode is

a) Maximum resistance of device

b) Resistance at q-point

c) Resistance at static points

d) Minimum resistance of a diode

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Answer: b [Reason:] Static or DC resistance of a diode is the resistance offered by a diode at its q-point. DC resistance represents steady state. That is, it is calculated by treating current and voltage as constants.

5. Average AC resistance and dynamic resistance are

a) Always Equal

b) Never equal

c) Both represents same quantity

d) calculated from V-I graph

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Answer: d [Reason:] Average AC resistance and dynamic or AC resistance are not exactly same. They both measures the resistance in a different way. AC resistance is slope of the tangent of the curve of characteristic graph at Q-point. But average AC resistance is measured by measuring the slope of straight line between limits of operation.

6. After cut-in voltage AC resistance of diode

a) Slightly decreases

b) Decreases exponentially

c) Slightly increases

d) Increases exponentially

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Answer: b [Reason:] After cut-in voltage current exponentially increases with small increase in voltage. This will considerably reduce resistance.

7. DC resistance of diode is measured at

a) Knee current

b) Cut-in voltage

c) Q-point

d) Reverse breakdown point

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Answer: c [Reason:] Static or DC resistance of a diode is the resistance offered by a diode at its q-point. DC resistance represents steady state. That is, it is calculated by treating current and voltage as constants.

8. Determine DC resistance of a diode described by characteristic graph at I_{D} = 10mA.

a) 9 Ω

b) 11.11 Ω

c) 10.10 Ω

d) 13.13 Ω

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Answer: a [Reason:] Static or DC resistance is the resistance of a diode at its operating point.
That is DC resistance = 0.9/10mA =9Ω.

9. For a diode, at 10mA DC resistance is 70Ω. The voltage corresponding to 10mA will be

a) 0.5V

b) 0.6V

c) 0.7V

d) 0.8V

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Answer: c [Reason:] Static or DC resistance is the resistance of a diode at its operating point.
Resistance = voltage/current
Therefore, voltage = current x resistance = 10mA x70 =0.7V

10. Calculate resistance of a diode at V_{D} = -10V from the characteristic graph given below

a) 1MΩ

b) 10MΩ

c) 15MΩ

d) 5MΩ

### View Answer

Answer: b [Reason:] Static or DC resistance is the resistance of a diode at its operating point.
Static resistance at -10V = 10V/current at -10V =10/1µA =10MΩ.