Using the traditional square-law model for MOSFET current-voltage characteristics, simple expressions are presented for predicting the performance of the basic CMOS inverter used in analogue CMOS technology. From these expressions, the low-frequency gain, the second- and third-harmonic distortion performance of the PMOS load, constant-current source load and push-pull inverters can be easily predicted by hand calculations. The results obtained by using these expressions are compared with previously published measurements and calculations.