Log domain hybrid design: block model and state space synthesis

Abstract

Log domain filters is a new member of current mode active continuous time filters, also known as ELIN (Externally Linear Internally Nonlinear) filters, ESS (Exponential State Space) filters and translinear filters. Log domain filters are suitable for low voltage/low power applications. The filters are highly linear, have tow distortion and are electronically tunable; advantages that make log domain filters interesting. Log domain filters use the idea of companding (Compressing and Expanding) signal processing. The designed first order lowpass filter is simulated in PSpice using the CBIC-R transistor model. The circuit supply voltage is selected to be 3V. The value for capacitances of the integrators is chosen to be 123pF. DC current sources are swept from 0.5µA to 80µA to tune the cutoff frequencies. Time domain and frequency domain analysis are performed.