Current mode high-frequency KHN filter employing differential class AB log domain integrator

In this study, a current mode log domain differential Class AB biquad filter based on Kerwin-Huelsman-Newcomb (KHN) structure has been synthesized by using the state-space method and by adopting translinear circuits. The proposed circuit can produce second-order low pass, band pass, high pass, all pass, and notch filter characteristics. The circuit is synthesized for high-frequency applications, i.e. around 100 MHz. The natural frequency and Q quality factor of the filter can be tuned electronically by varying the currents of current sources. Moreover, by varying currents of selected current sources, one can change the characteristics of the notch filter to generate general, low pass, and high pass notch filters. The designed circuit is simulated in both time domain and frequency domain in PSpice by using both idealized and NE 600 series type real transistors that are suitable for high-frequency operations. The frequency as well as time domain responses are found to be as expected. In addition to these simulations, THD and noise analysis are carried out. The details of obtained results are given. (C) 2008 Elsevier GmbH. All rights reserved.