1. The Collector feedback configuration is better than __________
a) Fixed Bias Configuration
b) Voltage divider configuration
c) C.E. configuration
d) C.B. configuration
Explanation: The fixed bias circuit has been seen to offer low stability with respect to change in ICO. The Voltage divider bias provides the most stable biasing mechanism. Hence, the collector feedback configuration is better than the fixed bias configuration while C.E. and C.B. are not biasing stages.
2. The Collector feedback is done by connecting a resistor from the collector to the __________
a) Emitter
b) Base
c) Supply voltage
d) Bias voltage
Explanation: The collector feedback configuration is done by connecting a resistor from the collector to the base voltage. This is done to stabilize the biasing voltage against thermal runaway
3. The Collector feedback configuration helps to stabilize __________
a) Bias voltage
b) Collector voltage
c) Bias current
d) Collector current
Explanation: The collector feedback configuration is used to stabilize the Collector current. The Collector current is seen to increase at a sincere rate which can harm the transistor by thermal runaway. Stabilizing this current is necessary during biasing a transistor for proper application.
4. The Collector feedback helps to evade __________
a) Inverse Active mode
b) Pinch Off
c) Thermal Runaway
d) Breakdown
Explanation: The increase in the Collector current is primarily due to ICO. A sudden increase in ICO can increase the Collector current and this will increase the temperature of the device. This is called thermal runaway and due to the high current gain of the transistor, the transistor can get destroyed due to thermal runaway. The Collector feedback configuration helps to evade this phenomenon
5. Due to the Collector feedback mechanism, the transistor remains always remains in the __________
a) Active mode
b) Saturation mode
c) Inverse Active
d) Cut-off
Explanation: The collector feedback configuration helps to keep the transistor in the active region. This is done because the bias voltage can get changed if the input and the bias voltage is superposed. With the introduction of this feedback mechanism, the transistor always stays biased in the active region
6. What are the effects on the output voltage if the Collector resistance increases in a Collector feedback configuration?
a) Not much effect
b) Bias voltage reduces
c) Bias voltage increases
d) Bias voltage doubles
Explanation: The increase in collector resistance doesn’t have much impact on the output voltage since the bias voltage is kept stable by the feedback operation. After all, one of the important applications of feedback is increasing stability and the output voltage is kept stable by this configuration.
7. From the base bias to the collector feedback configuration, the stability facto S reduces by a factor of __________
a) 1 + R1/(R1 + β)
b) 1 + β * R1/(R1 + β)
c) β * R1/(R1 + β)
d) R1/(R1 + β)
Explanation: This can be simply observed from the stability factors of both cases. The correct factor is 1 + β * R1/(R1 + β).
8. What is the stability factor against VBE for the collector feedback configuration?
a) β/(Rc * (1 + β))
b) -β/(RB + Rc * (1 + β))
c) β/(RB + Rc * (1 + β))
d) -β/(Rc * (1 + β))
Explanation: This is easily derived from the Collector feedback configuration by using the method of K.V.L. deriving a relation between the collector current and the base emitter voltage. It should be noted that the stability against VBE increases in comparison to the base bias comparison
9. Why are we worried about β during the Collector feedback configuration?
a) To maintain a stable q-point irrespective of β
b) To increase the gain
c) To decrease the output impedance
d) To maintain a stable input impedance
Explanation: If we change the device, β changes. But we want to keep the q-point stable so that circuit if represented as a black box, would provide the same characteristics and not be highly dependent on the transistor. Hence, we want to make the circuit insensitive to β.
10. The stability factors change from npn to pnp transistor.
a) True
b) False
Explanation: The stability factors are independent of whether the transistor is of npn or pnp type. It is only dependent on β and the impedance connected to the terminals of the transistor of a hyperbola.