The design of m. o. s. transistor operational-amplifier circuits, that can perform a variety of linear functions on digital and c. c. d. integrated circuits, is reviewed. Incorporating such structures monolithically leads to higher integration levels, and thereby to more effective systems realizations. The design approach is aimed at applications where low gains are required ( less than 10**3) with a bandwidth limit of 10 MHz. Slew rates of up to 5 V/ mu s can be designed and, by applying a chopper technique, drift figures below 1 mV may be obtained. Results are presented for two designs in p-m. o. s. and n-m. o. s. technology. The efficacy of the approach is demonstrated by operating the amplifiers as active filters and to effect c. c. d. transfer-function linearity improvements.