A SPICE macromodel for operational transconductance amplifiers

Operational transconductance amplifiers (OTAs) are now being used in the realization of continuous time active filters. The OTA can be used to simulate inductors and lossy integrators for ladder filter realizations or to realise grounded capacitor canonical structures of arbitrary transfer functions. Commercial applications include filters for HDTV operating at frequencies up to 20 MHz using MOS technology. Modern design techniques place heavy emphasis on circuit simulation to reduce hardware prototyping costs. Analogue systems based upon the operational amplifier (op-amp) as the active element have used macro models for many years. Macro models are used because they simulate the terminal characteristics of an op-amp with linear elements, rather than modelling the computationally intensive non-linear behaviour of a number of large transistor based circuits. Macro model based simulations are thus faster than non-linear simulations of an op-amp design saving design time and reducing development costs