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Practice each question, then open the answer or worked solution.
In the figure shows the transfer characteristics of a base biased CE transistor. Which of the following statements are true?
(b) At Vi = 1V, it can be used as an amplifier
(c) At Vi = 0. .5V, it can be used as a switch turned off
(d) At Vi = 2.5V, it can be used as a switch turned on
In an NPN transistor circuit, the collector current is 10mA. If 95 per cent of the electrons emitted reaches the collector, which of the following statements are true?
(b) The emitter current will be 10.53 mA
(c) The base current will be 0.53 mA
In the depletion region of a diode
(a) there are no mobile charges
(b) equal number of holes and electrons exist, making the region neutral
(c) recombination of holes and electrons has taken place
(d) immobile charged ions exist
(a) there are no mobile charges
(b) equal number of holes and electrons exist, making the region neutral
(d) immobile charged ions exist
What happens during regulation action of a Zener diode?
(a) The current in and voltage across the Zenor remains fixed
(b) The current through the series Resistance (Rs ) changes
(c) The Zener resistance is constant
(d) The resistance offered by the Zener changes.
(b) The current through the series Resistance (Rs ) changes
(d) The resistance offered by the Zener changes.
To reduce the ripples in a rectifier circuit with capacitor filter
(a) RL should be increased
(b) input frequency should be decreased
(c) input frequency should be increased
(d) capacitors with high capacitance should be used
(a) RL should be increased
(c) input frequency should be increased
(d) capacitors with high capacitance should be used
The breakdown in a reverse-biased p–n junction diode is more likely to occur due to
(a) large velocity of the minority charge carriers if the doping concentration is small
(b) large velocity of the minority charge carriers if the doping concentration is large
(c) strong electric field in a depletion region if the doping concentration is small
(d) strong electric field in the depletion region if the doping concentration is large
(a) large velocity of the minority charge carriers if the doping concentration is small
(d) strong electric field in the depletion region if the doping concentration is large
Very Short AnswersWhy are elemental dopants for Silicon or Germanium usually chosen from group XIII or group XV?
The elemental dopants for silicon or germanium is usually chosen from group XIII or group XV because the size of the dopant should be compatible with the semiconductor and they even form covalent bonds.
Sn, C, and Si, Ge are all group XIV elements. Yet, Sn is a conductor, C is an insulator while Si and Ge are semiconductors. Why?
Sn is a conductor because the energy gap for Sn is 0 eV, C is an insulator because the energy gap is 5.4 eV while Si and Ge are semiconductors because the energy gaps are 1.1 eV and 0.7 eV respectively. These energy gaps are related to their atomic size and that makes one conductor, the other insulator and the rest semiconductors.
Can the potential barrier across a p-n junction be measured by simply connecting a voltmeter across the junction?
No, the potential barrier across a p-n junction cannot be measured by simply connecting a voltmeter across the junction because the resistance of the voltmeter is very high.
Draw the output waveform across the resistor in the figure.
14.21 The amplifiers X, Y and Z are connected in series. If the voltage gains of X, Y and Z are 10, 20 and 30, respectively and the input signal is 1 mV peak value, then what is the output signal voltage (peak value) (i) if dc supply voltage is 10V?
(ii) if dc supply voltage is 5V?
Voltage gain in X = vx = 10
Voltage gain in Y = vy = 20
Voltage gain in Z = vz = 30
Total voltage amplification = vx.vy.vz = 6V
i) If dc supply voltage is 10V then the output voltage is 6V
ii) If dc supply voltage is 5V then the output voltage will exceed 5V