Subject: Basic VLSI Design

Topic: MOS Circuit Design Styles

Difficulty: Medium

4:1 mux using pass transistor logic

Advantages of using transmission gate logic.

• A CMOS transmission gate can be constructed by parallel combination of nMOS and pMOS transistors, with complementary gate signals.
• The main advantage of CMOS transmission gate compared to nMOS transmission gate is to allow the input signal to be transmitted to the output without the threshold voltage attenuation.
• It allows full rail transition i.e. ratioless logic
• The equivalent resistance is relatively constant during transition.
• Some gates are efficient implemented using transmission gate.