PMOS (P-channel Metal-Oxide-Semiconductor) transistors are commonly used in read multiplexers (read mux) for several reasons: also PMOS passes good logic 1 and bad logic 0

Why You Choose PMOS for Low-Power Design

Because PMOS transistors switch with a positive gate voltage, you find them ideal for applications where they spend most of the time in an “off” state. You can especially rely on them in static memory cells and other low-power circuitry.

Voltage compatibility

PMOS transistors have a lower threshold voltage compared to NMOS (N-channel Metal-Oxide-Semiconductor) transistors. This makes them more compatible with the voltage levels used in the read mux circuit.

Reduced leakage current

PMOS transistors have lower leakage currents compared to NMOS transistors. This is beneficial for power consumption, as it helps minimize the current flowing through the circuit when the transistors are in the off state.

Noise immunity

PMOS transistors have a higher noise immunity compared to NMOS transistors. This means they are less susceptible to noise interference, which can help improve the reliability and stability of the read mux operation.

Overall, the selection of PMOS transistors in a read mux is based on their voltage compatibility, lower leakage current, and better noise immunity characteristics, which make them suitable for the specific requirements of the circuit.

Why You Might Avoid PMOS Circuits

You’ll find PMOS designs come with drawbacks versus NMOS and CMOS options. You need multiple supply voltages (both positive and negative), you face higher power dissipation when conducting, and you deal with larger feature sizes. You’ll also notice their overall switching speed is slower.