Realization of Voltage-Mode and Current-Mode Electronically Tunable Universal Filters Employing Minimum Active and Passive Components
N. A. Shah and M. F. Rather
Two new universal filters each using two operational transconductance amplifiers (OTAs), a single unity cell and two capacitors are presented. The circuit in voltage-mode (VM) with three inputs and a single output supports the realization of the entire standard filtering functions from the same configuration at low output impedances. The circuit in current-mode (CM) with a single input and three outputs simultaneously implements lowpass (LP), bandpass (BP), and highpass (HP) responses all at high output impedances from which Notch and allpass (AP) signals can be implemented by simply connecting the appropriate node currents. Both the configurations have features of: minimum employment of active and passive elements, cascadibility to implement higher order transfer functions, devoid of resistors and matching conditions, orthogonal electronic tuning of the natural frequency (wo) and the bandwidth (wo/Q) and low active and passive sensitivities. The performance of the circuits is tested by using PSPICE simulation program.
Keywords: Analog filters, operational transconductance amplifier, voltage/currentmode active filters.