ABSTRACT
This chapter utilises the operational transconductance amplifier (OTA) to construct active filters. It presents systematic methods for generating second-order filters using a single OTA with a reasonable number of resistors and capacitors. These OTA filters are insensitive to tolerance and parasitics, of high frequency capability, electronically tunable, and simple in structure. The effects of OTA nonidealities such as finite input and output impedances and transconductance frequency dependence have also been considered for both discrete and integrated circuit filters. The chapter investigates OTA-C filters derived from the single OTA filters by resistor substitution. The OTA has two attractive features: its tranconductance can be controlled by changing the external dc bias current or voltage, and it can work at high frequencies. The OTA has been implemented widely in CMOS and bipolar and also in BiCMOS and GaAs technologies. Linearization techniques make the OTA able to handle input signals of the order of volts with nonlinearities of a fraction of one percent.
