What is the primary purpose of transistor biasing?
A Stabilize operation
B Signal modulation
C Control current
D Signal amplification
Transistor biasing is used to establish the correct operating point, or quiescent point (Q point), for a transistor. This ensures that the transistor operates in the desired region for stable and linear amplification.
What is the function of the emitter in a transistor?
A Control current
B Emit charge carriers
C Amplify signal
D Collect charge carriers
The emitter of a transistor is responsible for emitting charge carriers (electrons in NPN, holes in PNP) into the base. These charge carriers then move to the collector, allowing the transistor to amplify signals.
In common emitter configuration, what does the collector current depend on?
A Temperature
B Collector voltage
C Both base current and collector voltage
D Base current
In the common emitter configuration, the collector current is primarily determined by the base current. A small base current controls a much larger collector current, enabling amplification.
What is the main role of a bypass capacitor in amplifier circuits?
A Remove AC noise
B Stabilize frequency response
C Increase voltage gain
D Decrease current gain
A bypass capacitor is used in amplifier circuits to stabilize the AC signal by bypassing the emitter resistor. This allows the amplifier to achieve maximum voltage gain by removing negative feedback at high frequencies.
Which of the following best describes the active region of a transistor?
A Current controlled, linear amplification
B High current, low voltage
C No current flow
D Low current, high voltage
In the active region of a transistor, the current flow is controlled by the base current, and the transistor can amplify signals linearly. This region is essential for proper signal amplification.
What is the effect of increasing the base current in a transistor?
A Decreases collector current
B Increases emitter current
C Increases collector current
D No effect on collector current
The base current in a transistor controls the larger collector current. As the base current increases, the collector current also increases proportionally, enabling signal amplification.
What is the primary purpose of a coupling capacitor in amplifier circuits?
A Increase input impedance
B Stabilize biasing
C Control frequency response
D Block DC, pass AC
A coupling capacitor is used to connect amplifier stages while blocking DC components and allowing AC signals to pass through. This is essential in signal amplification, ensuring that only the desired AC signal is passed to the next stage.
What is the significance of the load line in transistor analysis?
A Defines the operating point
B Increases signal gain
C Determines power dissipation
D Stabilizes current flow
The load line is used to represent the constraints of the external circuit in transistor analysis. It defines the range of possible operating points (Q points) for the transistor, ensuring proper biasing and linear operation.
What does the term “saturation region” mean in the context of a transistor?
A Transistor is “off”
B Maximum current conduction
C Low voltage, high current
D High voltage, low current
The saturation region is when the transistor is fully on, and the current through the collector-emitter junction is at its maximum. In this region, the transistor acts as a closed switch, conducting maximum current.
What happens to the voltage gain of a common emitter amplifier if the emitter resistor is increased?
A Remains the same
B Increases
C Decreases
D Becomes zero
Increasing the emitter resistor in a common emitter amplifier increases negative feedback, which reduces the voltage gain. The emitter resistor stabilizes the operating point but at the cost of reduced amplification.
What is the purpose of the base resistor in a transistor circuit?
A Stabilize temperature
B Control current flow
C Prevent thermal runaway
D Control biasing current
The base resistor is used to control the amount of current flowing into the base of the transistor. It helps set the correct biasing point for stable operation and prevents excessive base current that could damage the transistor.
What is the primary difference between a common emitter and a common collector amplifier?
A Phase shift
B Input impedance
C Output impedance
D Amplification type
The primary difference is that a common emitter amplifier inverts the signal, creating a 180 degree phase shift, whereas a common collector amplifier provides no phase shift and is primarily used for impedance matching.
In a transistor, what is the role of the collector emitter voltage (VCE)?
A Amplify the input signal
B Determine transistor operating region
C Control current flow
D Set transistor biasing
The collector emitter voltage (VCE) determines the operating region of a transistor. It affects whether the transistor is in the active, saturation, or cutoff region, thus influencing its ability to amplify or switch signals.
What does the term “cutoff region” refer to in transistor operation?
A Minimum current flow
B Maximum current conduction
C No current flow
D Linear current flow
In the cutoff region, the transistor is “off,” meaning no current flows between the collector and emitter. The base emitter junction is not forward biased, and the transistor behaves like an open switch.
What is the primary function of feedback in transistor amplifiers?
A Improve stability
B Increase voltage gain
C Control biasing
D Reduce current gain
Feedback is used in transistor amplifiers to improve stability and linearity. It reduces distortion and helps maintain a consistent operating point, especially when the temperature or supply voltage changes.