In transmission gates, PMOS (P-channel Metal-Oxide-Semiconductor) and NMOS (N-channel Metal-Oxide-Semiconductor) transistors are often sized equally for specific reasons. Here’s why:
PMOS passes to good 1 and NMOS pass good 0
When we size the PMOS and NMOS transistors equally in transmission gates, it simplifies control, ensures you achieve balanced operation, and helps us get symmetrical performance. By doing this, we optimize the transconductance and enhance the design’s simplicity. These benefits allow us to create effective and reliable transmission gates for various digital circuit applications.
Simplifying Control: By sizing the PMOS and NMOS transistors equally, it simplifies the control mechanism of the transmission gate. Both transistors can be driven by the same control signal, making the circuit design more straightforward and efficient.
Balanced Operation: Equal sizing ensures balanced operation of the transmission gate. When the control signal is high, the PMOS transistor turns on, allowing the passage of signals from the input to the output. Simultaneously, the NMOS transistor turns off, preventing any signal interference or distortion. This balanced operation maintains signal integrity and minimizes signal degradation.
Symmetrical Performance: Equal sizing of PMOS and NMOS transistors helps achieve symmetrical performance characteristics. It ensures that both transistors have similar electrical properties, such as resistance and capacitance, leading to balanced signal propagation and improved overall circuit performance.