The parameters which can be obtained from output characteristics curves of common emitter BJT NPN transistor is/are:

Explanation:

Parameters from Output Characteristics of Common Emitter BJT NPN Transistor

Definition: The output characteristics of a common emitter (CE) configuration of a Bipolar Junction Transistor (BJT) refer to the relationship between the collector current (I_C) and the collector-emitter voltage (V_CE) for various levels of base current (I_B). These characteristics provide valuable information about the transistor's behavior and allow for the extraction of important parameters such as the forward current amplification factor (β) and the output resistance of the CE configuration.

Working Principle: In the CE configuration, the base-emitter junction is forward-biased, and the collector-base junction is reverse-biased. The base current (I_B) controls the larger collector current (I_C), which flows through the load connected in the collector circuit. By varying I_B, we can observe different levels of I_C for different values of V_CE, resulting in the output characteristics curve.

The output characteristics curve consists of three distinct regions:

• Cutoff Region: In this region, both the base-emitter and collector-base junctions are reverse-biased, and the collector current is negligible (approximately zero).
• Active Region: The transistor operates as an amplifier in this region, where the base-emitter junction is forward-biased, and the collector-base junction is reverse-biased. The collector current is directly proportional to the base current.
• Saturation Region: In this region, both the base-emitter and collector-base junctions are forward-biased, and the collector current reaches its maximum value, limited by the supply voltage and load resistance.

Correct Option Analysis:

The correct option is:

Option 4: Forward current amplification factor and output resistance of CE configuration.

This is the correct option because the following parameters can be obtained from the output characteristics of a common emitter BJT NPN transistor:

• Forward Current Amplification Factor (β): This is the ratio of the collector current (I_C) to the base current (I_B) in the active region of the transistor. Mathematically, it is expressed as:

β = I_C / I_B

• The value of β can be determined from the slope of the I_C versus I_B graph in the active region.
• Output Resistance (R_O): This is the reciprocal of the slope of the output characteristics curve (I_C versus V_CE) in the active region. It indicates how much the collector current changes with a change in collector-emitter voltage. Mathematically, it is expressed as:

R_O = ΔV_CE / ΔI_C

• The output resistance is an important parameter in analyzing the voltage gain of a CE amplifier circuit.

Thus, both the forward current amplification factor (β) and the output resistance (R_O) can be directly obtained from the output characteristics of a common emitter BJT.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Forward current amplification factor and input resistance of CE configuration.

This option is incorrect because, while the forward current amplification factor (β) can be determined from the output characteristics, the input resistance of the CE configuration cannot be obtained from these curves. The input resistance is determined from the input characteristics curve (I_B versus V_BE) and not from the output characteristics.

Option 2: Input resistance of CE configuration only.

This option is incorrect because the input resistance of the CE configuration is not derived from the output characteristics curve. The input resistance is related to the input characteristics (I_B versus V_BE) and is calculated as:

R_in = ΔV_BE / ΔI_B

Option 3: Output resistance of CE configuration only.

This option is partially correct, as the output resistance (R_O) can indeed be obtained from the output characteristics. However, it neglects the forward current amplification factor (β), which is also an essential parameter derived from the same characteristics. Therefore, this option is incomplete.

Conclusion:

The output characteristics of a common emitter BJT NPN transistor provide crucial information about the transistor's behavior. From these curves, the forward current amplification factor (β) and the output resistance (R_O) can be obtained, as explained in detail above. These parameters are vital for designing and analyzing transistor-based amplifier circuits, making option 4 the correct choice.