#CMOSInverter
#LogicGate
#DigitalCircuits
#ComplementaryMOS
#MOSFET
#IntegratedCircuits
#SemiconductorDevices
#ElectronicsDesign
#VLSI
#DigitalLogic
A CMOS inverter, short for Complementary Metal-Oxide-Semiconductor inverter, is a fundamental logic gate used in digital integrated circuits. It consists of both n-channel and p-channel MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) connected in a complementary configuration. The CMOS inverter performs the logical inversion of its input signal.
Here's a step-by-step explanation of the working of a CMOS inverter:
Circuit Configuration: A CMOS inverter consists of an n-channel MOSFET (NMOS) and a p-channel MOSFET (PMOS) connected in series between the power supply (VDD) and the ground (GND). The input signal (Vin) is connected to the gates of both transistors, and the output (Vout) is taken from the connection point between the transistors.
Input High (Logic 1): When the input voltage (Vin) is at a logic high level (typically VDD or a positive voltage), the PMOS transistor is in the "off" state (cut-off), and the NMOS transistor is in the "on" state (saturated).
PMOS: Since Vin is high, the voltage at the gate of the PMOS transistor is low (close to GND). This low gate voltage turns off the PMOS transistor, creating a high impedance between VDD and the output (Vout).
NMOS: With Vin high, the voltage at the gate of the NMOS transistor is also high (close to VDD). This high gate voltage turns on the NMOS transistor, creating a low resistance path between the output (Vout) and GND.
As a result, the output (Vout) is pulled down to the logic low level (GND) because of the NMOS transistor's conducting state.
Input Low (Logic 0): When the input voltage (Vin) is at a logic low level (typically GND or a low voltage), the NMOS transistor is in the "off" state, and the PMOS transistor is in the "on" state.
NMOS: As Vin is low, the voltage at the gate of the NMOS transistor is low (close to GND). This low gate voltage turns off the NMOS transistor, creating a high impedance between the output (Vout) and GND.
PMOS: With Vin low, the voltage at the gate of the PMOS transistor is high (close to VDD). This high gate voltage turns on the PMOS transistor, creating a low resistance path between VDD and the output (Vout).
Consequently, the output (Vout) is pulled up to the logic high level (VDD) because of the PMOS transistor's conducting state.
Transition Region: During the transition between logic high and logic low input levels, both transistors can be partially conducting for a short duration. This overlapping region helps avoid glitches or unwanted intermediate voltage levels at the output.
In summary, a CMOS inverter operates by using complementary pairs of transistors to invert the input logic level at the output. The PMOS transistor ensures a high output when the input is low, and the NMOS transistor ensures a low output when the input is high. This arrangement provides a high noise immunity, low static power consumption, and allows for efficient implementation of complex digital circuits.
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