Which terminal of a transistor controls the flow of current between the other two terminals?
A Base
B Collector
C Emitter
D Gate
In a Bipolar Junction Transistor (BJT), the base terminal controls the current flow between the collector and emitter. A small base current controls a larger current through the collector-emitter path.
What is the main function of a Zener diode?
A Signal amplification
B Voltage regulation
C Current rectification
D Frequency filtering
A Zener diode operates in reverse bias in the breakdown region, maintaining a constant output voltage despite variations in the input voltage or load.
Which transistor configuration provides the lowest output impedance?
A Common Base
B Common Emitter
C Common Collector
D Darlington Pair
The common collector configuration, also called an emitter follower, provides low output impedance, making it ideal for impedance matching.
What is the main advantage of a Field Effect Transistor (FET) over a Bipolar Junction Transistor (BJT)?
A Higher current gain
B Higher input impedance
C Better thermal stability
D Lower output impedance
FETs have very high input impedance because their gate terminal is insulated from the channel, making them ideal for applications requiring minimal loading of the input signal.
Which type of diode is used in rectifier circuits?
A Schottky diode
B LED
C PN junction diode
D Tunnel diode
PN junction diodes are used in rectifier circuits because they allow current to flow in one direction and block it in the opposite direction, converting AC to DC.
What is the typical value of the voltage drop across a germanium diode in forward bias?
A 0.3 V
B 0.7 V
C 1.1 V
D 0 V
Germanium diodes have a lower forward voltage drop of about 0.3 V, compared to silicon diodes with a typical drop of 0.7 V.
Which of the following is a unipolar device?
A FET
B BJT
C SCR
D Diode
Field Effect Transistors (FETs) are unipolar devices because they operate using only one type of charge carrier (either electrons or holes), unlike BJTs, which use both.
What is the function of an emitter bypass capacitor in a common emitter amplifier?
A To stabilize DC voltage
B To increase AC gain
C To block AC signals
D To reduce input impedance
The emitter bypass capacitor shorts AC signals to ground, preventing AC signal loss across the emitter resistor, thereby increasing the AC gain.
What does the term “slew rate” refer to in an op-amp?
A The maximum rate of change of the output voltage
B The maximum input voltage
C The gain-bandwidth product
D The noise level
Slew rate specifies the maximum rate at which an op-amp can change its output voltage, typically measured in volts per microsecond (V/μs).
Which amplifier class has the highest efficiency?
A Class A
B Class B
C Class AB
D Class D
Class D amplifiers, also known as digital amplifiers, are highly efficient (up to 90% or more) because they operate using switching techniques that minimize power loss.
In a BJT, which region is reverse-biased during normal active operation?
A Base-Emitter junction
B Base-Collector junction
C Emitter-Collector junction
D All junctions
In active mode, the base-emitter junction of a BJT is forward-biased, and the base-collector junction is reverse-biased, enabling amplification.
What type of circuit is used to produce a square wave from a sinusoidal input?
A Integrator
B Differentiator
C Schmitt Trigger
D Voltage regulator
A Schmitt Trigger converts a sinusoidal input into a square wave by using hysteresis to define distinct switching points.
What is the role of a coupling capacitor in amplifier circuits?
A To stabilize the circuit
B To block DC while allowing AC signals to pass
C To amplify the signal
D To match impedance
Coupling capacitors are used to separate AC signals from DC bias components, enabling the signal to pass between stages without altering the DC operating point.
What is the function of a voltage regulator IC like 7805?
A To provide variable voltage
B To provide a fixed +5 V output
C To amplify current
D To filter noise
The 7805 is a fixed voltage regulator IC that provides a stable +5 V output regardless of variations in input voltage or load.
Which type of amplifier is used to amplify low-level differential signals?
A Differential amplifier
B Common emitter amplifier
C Voltage follower
D Power amplifier
Differential amplifiers amplify the difference between two input signals, rejecting common-mode signals such as noise.