Q.30
Define logic gate and explain why NOT gate is called an inverter.
The transistor is in the common emitter configuration. Its DC current gain is 50. If collector current is 3 mA, calculate the base current.
Best answer
Answer: Base current \(I_B = 0.06\) mA \(= 60\ \mu\)A.
(i) Logic gate: A logic gate is a digital electronic circuit with one or more inputs and only one output, in which the output is related to the inputs by a definite logical relationship (Boolean algebra). Inputs and outputs take only two levels, 0 (low) and 1 (high).
NOT gate as inverter: A NOT gate has one input A and one output Y, with \(Y = \overline{A}\). Its truth table is:
| Input A | Output Y |
|---|---|
| 0 | 1 |
| 1 | 0 |
The output is always the opposite (complement) of the input: a high input gives a low output and a low input gives a high output. Because it inverts the logic level, the NOT gate is called an inverter.
(ii) Numerical: \(\beta_{dc} = \dfrac{I_C}{I_B}\)
\[I_B = \frac{I_C}{\beta_{dc}} = \frac{3\ \text{mA}}{50} = 0.06\ \text{mA} = 60\ \mu\text{A}\]Log in or create a free account to answer this question.
