CMOS XOR Gate

Symbol

Information

A CMOS XOR Gate is a fundamental digital logic gate that implements logical exclusive disjunction. The output is HIGH (OH) when the inputs are different, and LOW (OL) when the inputs are the same.

The gate operates based on voltage thresholds:

• If the inputs are different (one HIGH and one LOW), the output is HIGH (OH).

• If the inputs are the same (both HIGH or both LOW), the output is LOW (OL).

• Intermediate voltages are not handled explicitly in this model.

Ports

• In1: First input terminal

• In2: Second input terminal

• Out: Output terminal

Model

The CMOS XOR Gate model implements standard XOR logic behavior using voltage thresholds.

Attributes:

• Vin1 (signal): Input voltage at In1

• Vin2 (signal): Input voltage at In2

• Vout (signal): Output voltage at Out

• IL (param): Input LOW voltage threshold (default: 0.2V)

• IH (param): Input HIGH voltage threshold (default: 3.2V)

• OL (param): Output LOW voltage (default: 0.0V)

• OH (param): Output HIGH voltage (default: 5.0V)

Methods:

• analog(): Defines the XOR gate behavior based on voltage thresholds.

Logic Table

Vin1	Vin2	Vout
LOW	LOW	LOW
LOW	HIGH	HIGH
HIGH	LOW	HIGH
HIGH	HIGH	LOW

Python

from pyams.lib import model, signal, param, voltage

class CXOR(model):
    """
    CMOS XOR Gate model using voltage threshold logic.
    """
    def __init__(self, Out, In1, In2):
        # Signal declarations
        self.Vin1 = signal('in', voltage, In1)
        self.Vin2 = signal('in', voltage, In2)
        self.Vout = signal('out', voltage, Out)

        # Parameter declarations
        self.IL = param(0.2, 'V', 'Input LOW voltage threshold')
        self.IH = param(3.2, 'V', 'Input HIGH voltage threshold')
        self.OL = param(0.0, 'V', 'Output LOW voltage')
        self.OH = param(5.0, 'V', 'Output HIGH voltage')

    def analog(self):
        """Defines the XOR gate behavior using voltage threshold logic."""
        if (self.Vin1 <= self.IL and self.Vin2 >= self.IH) or \
           (self.Vin1 >= self.IH and self.Vin2 <= self.IL):
            self.Vout += self.OH  # Output HIGH when inputs are different
        else:
            self.Vout += self.OL  # Output LOW when inputs are the same

Command Syntax

The syntax for defining a CMOS XOR gate in a PyAMS simulation:

# Import the model
from pyams.models import CXOR

# CXOR instance creation
# Out, In1, In2: Connection points in the circuit
xor_gate = CXOR(Out, In1, In2)