OR Gate Circuit Diagram by using transistor

Answer 1

Here is a circuit diagram of an OR gate using transistors:

```
+---------+
| |
Input-A| |
| Q1 |--- Output
Input-B| ____|
| |
+---->| Q2
|
__|__
___|
|
|
__|__
___
_| |
|___|

```

Explanation:
- The inputs A and B are connected to the base terminals of transistors Q1 and Q2, respectively.
- The emitters of both transistors Q1 and Q2 are connected to the ground (0V).
- The collector of transistor Q1 is connected to the output terminal.
- The collector of transistor Q2 is also connected to the output terminal.
- The output is taken from the junction of the collector terminals of Q1 and Q2.

Working:
- When input A is HIGH (logic 1), transistor Q1 is turned ON and allows current to flow through its collector-emitter path, resulting in a LOW output (logic 0).
- Conversely, when input A is LOW (logic 0), transistor Q1 is turned OFF, and no current flows through its collector-emitter path. In this case, the output is determined by input B.
- When input B is HIGH (logic 1), transistor Q2 is turned ON and allows current to flow through its collector-emitter path, resulting in a LOW output (logic 0).
- If both inputs A and B are LOW (logic 0), both transistors Q1 and Q2 will be turned OFF, and no current flows through the output terminal. The output in this case will also be LOW (logic 0).
- When either input A or input B (or both) is HIGH (logic 1), the corresponding transistor(s) turn(s) ON, allowing current to flow through the output terminal. The output in this case will be HIGH (logic 1).

Note:
- In this circuit, NPN transistors are used. If you want to implement this circuit using PNP transistors, you can use a similar approach but with opposite polarities and connections.