Consider the following statements regarding an N-P-N Bipolar Junc
Consider the following statements regarding an N-P-N Bipolar Junction Transistor:
1. Emitter diode is forward biased and the collector diode is reverse biased
2. Emitter has many free electrons
3. Free electrons are injected into the base and pass through the collector
4. Depletion layers around junction J1 and J2 of BJT are widened.
Which of the above statements are correct?A. 1, 2 and 4
B. 1, 3 and 4
C. 2, 3 and 4
D. 1, 2 and 3
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
Explanation:
N-P-N transistor
The schematic of the N-P-N transistor is shown below
KVL for the junction voltages
- VBE – VCB + VCE = 0
VCE = VBE + VCB
KCL for the transistor is
IE = IB + IC
From the schematic, it is clear that the Emitter diode is forward biased and the collector diode is reverse biased.
Statement I is true
The current components in a transistor are shown below
DIAGRAM CURRENT COMPONENTS
This shows the junction voltages and currents in one place.
In N-P-N transistor the emitter is n-type so the majority charge carriers will be electrons.
Statement II is true.
When the supply is given externally the charge carriers start moving and some of them recombine at the base and remaining will pass through the collector of the transistor which is largest.
Statement III is true.
- We know that junction width depends on the region of operation.
- If the diode is in the forward bias then the junction width will be small.
- If the diode is in reverse bias the junction width is large.
In the statement it is given that both the junctions are widened, this implies that both are reverse biased which is false.
