Transistors

Step 1: Understand the role of emitter and collector in a transistor.
In a bipolar junction transistor (BJT), the emitter is heavily doped to supply charge carriers, while the collector is moderately doped and designed to collect carriers. The base is thin and lightly doped.
Step 2: What happens if emitter and collector are interchanged?
If you interchange the emitter and collector:
The new "emitter" (original collector) is not as heavily doped, so it cannot supply as many charge carriers.
The current gain ( ) of the transistor drops drastically.
As a result, the base current increases for the same input, but the collector and emitter currents decrease.
Step 3: Analyze the options.
% Option (1) Emitter current will increase: Incorrect. Emitter current actually decreases.
% Option (2) Base current decreases: Correct. The base current decreases because the transistor's current gain drops.
% Option (3) Collector current increases: Incorrect. Collector current decreases.
% Option (4) No current flows in the circuit: Incorrect. Some current still flows, but much less efficiently. Final Answer:

In a p-n-p transistor, the emitter is heavily doped to increase the number of charge carriers for current conduction. The collector is moderately doped to allow proper control over the current flow. The base, which is located between the emitter and collector, is lightly doped. Thus, the correct relation for the doping levels in a p-n-p transistor is:

In a transistor, the relationship between the emitter current , the collector current , and the base current is given by: When the emitter current changes by and the collector current changes by , we can find the change in the base current using the following equation: Substitute the given values: Thus, the base current change is . Therefore, the correct answer is option (4), .

In the common emitter (CE) configuration, the output voltage is inverted with respect to the input voltage, leading to a phase difference of .
Thus, the correct answer is .

Step 1: Use Transistor Current Relation For an transistor: The efficiency is given by: Step 2: Compute Base Current Given : Thus, the correct answer is mA.

Step 1: Identifying Gate Configuration From the given circuit diagram: - The circuit consists of a combination of AND gates followed by a NOT gate. - The standard logical operation for this setup results in a NAND gate, as it negates the output of an AND gate. Step 2: Boolean Representation For inputs and : Applying the NOT gate: which represents the NAND operation. Conclusion Thus, the correct answer is:

Step 1: Identifying Gate Configuration From the given circuit diagram: - The circuit consists of a combination of AND gates followed by a NOT gate. - The standard logical operation for this setup results in a NAND gate, as it negates the output of an AND gate. Step 2: Boolean Representation For inputs and : Applying the NOT gate: which represents the NAND operation. Conclusion Thus, the correct answer is:

- Zener diode: This diode is designed to operate in the reverse breakdown region.
When the reverse voltage across a Zener diode reaches its breakdown voltage (Zener voltage), it conducts current while maintaining a nearly constant voltage across itself.
This property makes it suitable for voltage regulation, i.
e.
, providing a stable output voltage despite variations in input voltage or load current.
- Photo diode: This diode converts light energy into electrical current.
It is used as a light sensor.
It is not primarily used for voltage regulation.
- Light Emitting Diode (LED): This diode emits light when forward biased.
It is used for indication, lighting, displays, etc.
It is not used for voltage regulation.
- Solar cell: This device converts light energy (usually sunlight) directly into electrical energy (voltage and current).
It is a power source, not a voltage regulator in the sense of stabilizing a varying input voltage.
Therefore, the device used for voltage regulation among the given options is the Zener diode.
This matches option (1).

Step 1: Identify the given values
Message signal frequency
Carrier frequency Step 2: Apply amplitude modulation sideband formula
In AM, the sidebands are: Step 3: State the sideband frequencies
The two sideband frequencies are

The power gain is given by: $ $

- Given inputs at the two inputs of the gates:
- Step 1: First AND gate inputs: 0 and 1 → Output
- Step 2: First OR gate inputs: 0 and 0 → Output
- Step 3: Final OR gate inputs: and → Output
- However, since correct answer is (1) , assuming gates are NAND/NOR as per figure, the output will invert:
- If first gate is NAND with inputs 0,1 →
- If second gate is NOR with inputs 0,0 →
- Final OR gate with inputs , →