Fifth Order Butterworth Low Pass Square-Root Domain Filter Design

摘要

Interest in translinear circuits has rapidly increased recently [1, 2]. Translinear circuits have low supply voltage, low power consumption, high dynamic range and low noise performance [2, 3]. Square-root domain (SRD) circuits are subclass of translinear circuits and externally linear internally nonlinear (ELIN) circuits. ELIN circuits are suitable for low voltage applications and low power dissipation [3, 4]. SRD circuits use the MOSFET devices in the strong inversion region of operation, and thus are based on the quadratic relationship between gate-to-source voltage and drain current [5, 6], SRD circuits use compounding in signal processing. Therefore, SRD circuits have large dynamic ranges at low supply voltages [1, 3]. In the last decades, SRD filtering has become very popular and many studies have been presented in this issue [7-10]. In this study, a fifth order low pass Butterworth filter is designed with two different approaches having same transfer function by using state space synthesis method. First of all, fifth order state space system equations obtained from the transfer function are considered. Secondly, system is considered as compose of two second order and one first order transfer functions. Therefore, three set of system equations are cascaded to obtain a fifth order filter. Both filters are designed by using state space synthesis method and designed circuits are analyzed with PSpice. Obtained frequency, THD and noise analysis results are presented.