CMOS first-order current-mode all-pass filter with electronic tuning capability and its applications

Abstract

In this paper, a novel first-order current-mode (CM) electronically tunable all-pass filter including one grounded capacitor and two dual-output current followers (DO-CFs) is presented. The used DO-CFs are implemented using only 10 MOS transistors granting the proposed CM all-pass filter extremely simple structure. The proposed filter is suitable for integrated circuit (IC) fabrication because it employs only a grounded capacitor and is free from passive component matching conditions. Interestingly the introduced configuration uses minimum number of components compared to other works. It also offers other interesting advantages such as, alleviating all disadvantages associated with the use of resistors, easy cascadability and satisfies all technology requirements such as small sizing, simple realization, low voltage and low power operation. Additionally, the circuit parameters can be easily set by adjusting control voltages. Most favorably, the proposed CM all-pass filter can be simply used as a voltage-mode (VM) all-pass filter with outstanding properties of adjustable gain and tunability. To further show the versatility of the proposed structure a sinusoidal oscillator is also derived from presented CM all-pass filter. Nonideal gain and parasitic impedance effects on developed CM filter are discussed. Finally, simulation results with SPICE program are included to confirm the theory. © 2013 World Scientific Publishing Company.