Single-CDTA (Current Differencing Transconductance Amplifier) Current-Mode Biquad Revisited

This paper presents a current-mode (CM) second-order filter, employing one so-called “Z Copy – Current Differencing Transconductance Amplifier” (ZC-CDTA), two grounded capacitors, and one virtually grounded resistor. The filter provides two current outputs of low-pass (LP) and band-pass (BP) types for driving independent loads, and one high-pass (HP) current output, flowing through one of the working capacitors. Other implementations of various types of transfer functions are proposed by means of commonly used methods of input/output current summing. Their critical analysis is accomplished from the point of view of tracking errors and dynamic range optimization. Results of the PSpice simulation, which utilizes the CDTA model on the level of CMOS transistor structure, are enclosed.