Current mode tow-thomas biquadratic differential class AB log domain filter

Abstract

In this study, a current-mode Class AB differential type Tow-Thomas filter has been synthesized in the log domain by using the state space method and by adopting translinear circuits. Varying the values of the current sources of the circuit, the pole frequency of the filter as well as the quality factor and DC gain of the circuit can be tuned electronically. The circuit was simulated in PSpice for both idealized transistor models and CBIC-R type transistors. We are able to tune the pole frequency between 50 kHz and 5 MHz, precisely two decades, and we can easily set the quality factor of circuits electronically to various values between 0.5 and 7. In this work, a high dynamic range is achieved within 4 decade change in Ipeak/Ibias. The proposed circuit has unity gain and independent of Q quality factor for the band pass filter response. All simulation results are verified by THD analysis. Our results show that the measured total harmonic distortions under the %2. We also performed noise analysis. Various simulations results are presented to show the effectiveness of the proposed circuit. Copyright © 2009 Praise Worthy Prize S.r.l.