4 bit barrel shifter

How it works

1. 1Designed a 2x1 multiplexer from transmission gates, then a 4x1 multiplexer from three of them
2. 2Built the shifter from four 4x1 multiplexers, with S1 and S0 setting how far the word rotates
3. 3Compared the design against the same circuit built from universal gates
4. 4Simulated at transistor level in LTspice on 180 nm models at 1.8 V, and designed in Cadence Virtuoso

Result

Each 4x1 multiplexer needs 18 transistors instead of 54, so the whole shifter uses 72 transistors instead of 216, with lower power.