1. For an ideal diode which of the following is true?
a) It allows the passage of current in the forward bias with zero potential drop across the diode
b) It does not allow the flow of current in reverse bias
c) All of the mentioned
d) None of the mentioned
Explanation: Both of the facts mentioned hold true for an ideal operational amplifier.
2. Diodes can be used in the making of
a) Rectifiers
b) LED lamps
c) Logic gates
d) All of the mentioned
Explanation: Diodes are used to make rectifiers (full wave or half wave rectifiers are the most common examples), LED lamps uses diodes (diodes are generally doped for their use in this purpose) and logic gates can also be made using diodes using the fact that diodes are conducting only in the forward biased configuration
3. For the connections shown below, the equivalent logic gate is
a) OR gate
b) AND gate
c) XOR gate
d) NAND gate
Explanation:The following circuit behaves as a OR logic gate
4. For the connections shown below, the equivalent logic gate is
a) OR gate
b) AND gate
c) XOR gate
d) NAND gate
Explanation: The circuit shown behaves as an AND logic gate.
5. The figure below shows a circuit for an AC voltmeter. It utilizes a moving-coil meter that gives a full-scale reading when the average current flowing through it is 1 mA. The moving-coil meter has a 50-Ω resistance. The value of R that results in the meter indicating a full-scale reading when the input sine-wave voltage VI is 20 V peak-to-peak is
a) 3.183 kΩ
b) 3.133 kΩ
c) 3.183 Ω
d) 56.183 Ω
Explanation:Average value of input voltage= 20/π or 6.366 V.
Since there is diode half of the time there is no voltage across the voltmeter hence the average value of the input voltage is 10/π or 3.183V.
The total resistance required to generate 1mA current is 3.183 kΩ out of which 50Ω is provided by the moving coil. Therefore, a resistance of 3.133 kΩ is required.
6. The units frequently used to measure the forward bias and reverse bias current of a diode are
a) µA and µA respectively
b) µA and mA respectively
c) mA and µA respectively
d) mA and mA respectively
Explanation: The currents in forward bias is generally in MA and in the reverse bias it is very small and is generally measured in µA
7. A diode
a) Is the simplest of the semiconductor devices
b) Has a characteristic that closely follows that of a switch
c) Is two terminal device
d) All of the mentioned
Explanation: Both the statements are true for a diode.
8. Which of the following is method to model a diode’s forward characteristics?
a) Iteration method
b) Graphical method
c) Constant-voltage drop model
d) All of the mentioned
Explanation: All of the mentioned are different methods used to model a diode’s forward characteristics.
9. A voltage regulator needs to provide a constant voltage in spite of the fact that there may be
a) Change in the load current drawn from the terminals of the regulator
b) Change of the DC power supply that feeds the regulator circuit
c) None of the mentioned
d) All of the mentioned
Explanation: Voltage regulators are required in both of the situations mentioned.
10. The value of the diode small-signal resistance rd at bias currents of 0.1 mA is
a) 250 Ω
b) 25 Ω
c) 2.5 Ω
d) 0.25 Ω
Explanation: Thermal voltage at room temperature is 25mV and the current is 0.1mA. rd = 25mV/0.1mA or 250 Ω.