why we can not use diode in logical gates

Diodes are not typically used as the primary active components in digital logic gates for several reasons:

1. Binary Logic: Digital logic gates work based on binary logic, where inputs and outputs are typically represented by two voltage levels (e.g., 0V and 5V in TTL logic). Diodes, on the other hand, are primarily used for analog applications, such as rectification and signal clipping. They do not provide the necessary voltage levels (0 and 1) required for binary logic.

2. Lack of Amplification: Diodes do not have the amplification capabilities needed to perform logical operations. Logic gates require the ability to amplify weak input signals to produce strong output signals, which diodes cannot do.

3. No Signal Inversion: Most digital logic gates have both inverted and non-inverted outputs (e.g., NOT gates provide both A and NOT A outputs). Diodes cannot provide signal inversion; they only allow current to flow in one direction.

4. Limited Functionality: Diodes have a limited set of functions (primarily allowing or blocking current flow) compared to active components like transistors, which can be used to implement a wide range of logical functions (AND, OR, NOT, NAND, NOR, XOR, etc.).

5. Noise Immunity: Digital logic gates often incorporate noise immunity features to ensure reliable operation in noisy environments. Diodes lack these noise immunity features, making them less suitable for digital logic applications.

For these reasons, transistors are the preferred choice for implementing digital logic gates. Bipolar junction transistors (BJTs) and field-effect transistors (FETs) are commonly used in integrated circuits to create various logic gates that can perform complex logical operations efficiently and reliably. Transistors can be used to amplify and switch signals, making them well-suited for digital logic applications.