Which of the following is true for the active region of an NPN transis...
The correct answer is option C: All of the mentioned.
Explanation:
In an NPN transistor, the active region refers to the operating mode where the transistor is being used as an amplifier. Let's discuss each option to understand why all of them are true for the active region of an NPN transistor.
a) The collector current is directly proportional to the base current:
In the active region, the NPN transistor is biased such that the base-emitter junction is forward biased and the base-collector junction is reverse biased. This biasing arrangement allows the transistor to operate as an amplifier.
When a small current, known as the base current (IB), flows into the base-emitter junction, it causes a much larger current, known as the collector current (IC), to flow through the collector-emitter junction. This relationship between the base current and the collector current is typically described by the current gain factor, β (beta), which is the ratio of IC to IB. In the active region, β is usually greater than 1, indicating that the collector current is indeed directly proportional to the base current.
b) The potential difference between the emitter and the collector is less than 0.4 V:
In the active region, the transistor operates with a voltage drop across the collector-emitter junction. This voltage drop is typically referred to as VCE (collector-emitter voltage) and is generally greater than 0.2 V.
However, the option states that the potential difference between the emitter and the collector is less than 0.4 V. This statement is not entirely accurate as the actual voltage drop depends on the specific transistor and its operating conditions. It can vary significantly based on the biasing arrangement and the load connected to the collector.
c) All of the mentioned:
As explained above, option a is true because the collector current is indeed directly proportional to the base current. However, option b is partially incorrect, as the potential difference between the emitter and the collector is not specifically limited to less than 0.4 V.
Therefore, only option a is completely accurate, while option b is partially accurate. Hence, the correct answer is option C: All of the mentioned.