An m. o. s. operational amplifier suitable for large-scale integration using n-channel enhancement-depletion technology is reported. It has a large gain of 94 dB, a unity-gain bandwidth of 1 MHz with a small power dissipation of 2. 4 mW and it occupies only 0. 2 mm**2. These miniaturized amplifiers require computer aided design, and the capabilities of the nonlinear d. o. m. o. s. model and computer program are demonstrated. Simple equations for exploratory design and comparison with designs using weak-inversion, complementary or bipolar transistors are also discussed.