Design and Automation of Bi-Quad Filter Using High Performance Operational Transconductance Amplifier (OTA) with nMOS Diode Connected Load Resistor

Bi-Quad filter is a type of active-c filter. It is constructed using two-integrator-loop type topology. The two-integrator-loop topology is derived from rearranging a bi-quadratic transfer function. The rearrangement will equate one signal with the sum of another signal, its integral, and the integral's integral. In other words, the rearrangement reveals a state variable filter structure [1]. By using different states as outputs, any kind of second-order filter can be implemented. This Filter is designed using three OTAs (Operational Transconductance Amplifiers) which are controllable by three voltages. By controlling the inputs to these control voltages, any kind of filter can be implemented. In this work, low pass, high pass, band pass, notch and all pass filters is designed and implemented using a single Bi-Quad filter [2]. The Filter is also automated to generate various design parameters. Construction of these filters is performed in this paper using high performance OTA. Active Resistor for this can be designed using either 2-NMOS diode connected load or using grounded OTA.

Since OTA consumes lot of area, Active-R is chosen to be designed using NMOS diode connected MOSFETs in this paper.The high performance OTA will provide high bandwidth, high linearity and wide tuning range, which is not possible with the conventional OTA. Design of Conventional OTA [3] and High performance OTA is done and they are checked for linearity, slew rate and total harmonic distortion. From the results it was seen that High performance OTA will perform in much better way when compared to Conventional OTA. High performance OTA is used to realize the Bi-Quad Filter. Experimental results verifying the performances of the high performance OTA and experimental results of various filters using Bi-Quad filter along with it’s automation are presented. All the designs are implemented using tanner EDA and technology file used is 130nm. As an application example of bi.