# Electronic Devices and Circuits Questions and Answers – Physical Model of a CB Transistor

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Physical Model of a CB Transistor”.

1. Where is the input measured in a common base transistor physical model?
a) Collector terminal
b) Emitter terminal
c) Base terminal
d) Ground

Explanation: In the physical model of a common base transistor amplifier the input is measured at the emitter terminal of the BJT biased device. Whereas, the output is measured across the collector terminal of the biased BJT device.

2. Which parameter of the physical model is varied while measuring the input characteristics of a common-base transistor?
a) Emitter current
b) Emitter voltage
c) Collector current
d) Emitter base voltage

Explanation: To determine the input characteristics, the collector-base voltage is kept constant at zero volts and the emitter base voltage is increased from zero volts to different voltage levels. For each voltage level of the input voltage, the input current is recorded.

3. Where is the output measured in a common base transistor physical model?
a) Collector terminal
b) Emitter terminal
c) Base terminal
d) Ground

Explanation: In the physical model of a common base transistor amplifier the output is measured at the collector terminal of the BJT biased device. Whereas, the input is measured across the emitter terminal of the biased BJT device.

4. Which parameter of the physical model is varied while measuring the output characteristics of a common-base transistor?
a) Emitter current
b) Emitter voltage
c) Collector current
d) Collector base voltage

Explanation: To determine the output characteristics, the emitter current is kept constant at zero and the collector base voltage is increased from zero volts to varying voltage levels. For each voltage level of the output voltage, the collector current is recorded.

5. What is the path of the output characteristic of a CB transistor physical model in the active region?
a) Linear
b) Exponential decrease
c) Exponential increase
d) Constant

Explanation: In a physical model of a common base transistor, the output characteristic curve first increases exponentially and then remains constant. In the active region of working the output characteristics show a constant value collector current with respect to collector base voltage.

6. What is the path of the output characteristic of a CB transistor physical model in the saturation region?
a) Linear
b) Exponential decrease
c) Exponential increase
d) Constant

Explanation: In a physical model of a common base transistor, the output characteristic curve first increases exponentially and then remains constant. In the saturation region of working the output characteristics show an exponential increase in the collector current with respect to collector base voltage.

7. What is the path of the input characteristic of a CB transistor physical model?
a) Linear
b) Exponential decrease
c) Exponential increase
d) Constant

Explanation: In a physical model of a common base transistor, the input characteristic curve increases exponentially. The emitter current increases exponentially with respect to emitter base voltage for fixed values of collector base voltage.

8. How do you calculate the dynamic input resistance of a CB transistor?
a) ΔVBE / ΔIC
b) ΔVBE / ΔIE
c) ΔVCB / ΔIC
d) ΔVCB / ΔIE

Explanation: Dynamic input resistance is defined as the ratio of change in emitter base voltage to the corresponding change in the emitter current. While the collector voltage is kept at a constant value. Therefore, ri = ΔVBE / ΔIE.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits. 