Universal filter and its oscillator modification employing only active components

An active-only devices current-mode universal filter using the biquadratic transfer function is proposed. The proposed circuit is realized based on minimized active-only components count without external passive elements. The electronic resistors are used instead of 2 OTAs. The different kinds of filter function such as lowpass, highpass, bandpass and band-reject response can be obtained without changing circuit topology. A quadrature oscillator can also be easily modified without changing circuit topology. The proposed circuit is realized by using 4 MOS transistors, 3 OTAs, and 2 Opamps. The parameters omega_P and Q_P can be electronically tuned independently through adjusting the transconductance gains of the OTAs. The simulation results are given by PSpice.