Log-domain synthesis of nth order universal filter

In this paper a synthesis approach for an nth-order universal log-domain filter comprising lowpass (LP), highpass (HP) and bandpass(BP) filtering functions is proposed. The approach is simple and the method of extending the approach to two uncommon filtering functions, lowpass notch (LPN) and high pass notch (HPN), is also given. The second, fourth and sixth-order universal log-domain filters are designed using log-exponential relationship between voltage and current of bipolar junction transistors (BJT) for the verification of approach. The performance of proposed universal filter and that of extended LPN and HPN was verified through simulation results.