Abstract: A method of compensating a monolithic integrated operational amplifier against process and temperature variations, such that the operational amplifier is suitable for use in an active filter, the method comprising a providing an amplifier having a first stage and an output stage, wherein the output stage drives an RC load, and wherein a compensation capacitor at an output of the first stage is selected so as to scale with the capacitance C of the RC load, and a transconductance of the first stage is a function of the resistance R of the RC load.

Abstract: A mixer core is provided which has a pair of CMOS transistors 21 and 22 connected as a matched pair and having a common source node N1. The CMOS transistors have a non-linear parasitic capacitance which degrades the harmonic performance of the mixer core. An inductor is connected to the common source node and optionally to ground, a signal input node or to a further common source node when the mixer core is part of a double balanced mixer. The inductor is chosen such that it co-operates with the parasitic capacitors to form a resonant circuit tuned to the local oscillator frequency or optionally a harmonic of it, such as the second harmonic, or to the input signal frequency.