The schematic of a CMOS inverter is:

 

The schematic of a CMOS inverter is:

1. _DD V_out V_in

2. _DD V_out V_in

3. _DD V_out V_in

4. _DD V_out V_in

Correct Answer: Option 2

Explanation:

A CMOS (Complementary Metal-Oxide-Semiconductor) inverter is constructed using a complementary pair of transistors: one PMOS (p-channel) and one NMOS (n-channel).

• PMOS Transistor: Connected between the supply voltage (V_DD) and the output (V_out). In schematic symbols, a PMOS is identified by a small circle (bubble) at the gate terminal, indicating that it turns on with a LOW signal.
• NMOS Transistor: Connected between the output (V_out) and the ground. It does not have a bubble at the gate, indicating it turns on with a HIGH signal.

Operation:

• When V_in is HIGH (1): The NMOS turns ON and the PMOS turns OFF. The output node is connected to ground, so V_out is LOW (0).
• When V_in is LOW (0): The PMOS turns ON and the NMOS turns OFF. The output node is connected to V_DD, so V_out is HIGH (1).

Diagram 2 correctly shows the PMOS on top (with bubble) and the NMOS on the bottom, which is the standard configuration for a CMOS inverter.

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