An Adjustable Dual-Output Current Mode MOSFET-Only Filter

Abstract

This brief presents an adjustable third-order filter without employing passive elements. The proposed filter combines two low-pass and band-pass MOSFET-only topologies to configure a dual-output structure, while the transconductances and parasitic gate-source capacitances of the transistors act as the required passive elements. The main core of the proposed filter contains just 3 transistors that with the elimination of passive elements results in a small silicon area and low power consumption. The proposed filter benefits from low-input and high-output impedances that is an advantage for cascading in current-mode systems. Moreover, a kind of self-biasing topology is used to configure the proposed filter in which a control voltage is provided to move the center frequency of both outputs in a wide frequency range. The proposed circuit was fabricated using TSMC 0.18 $\mu \text{m}$ CMOS process. Experimental and simulation results at a supply voltage of 1.8 V show a bandwidth range from 38.1 MHz to 99.5 MHz for a capacitive load bigger than 15 pF, while the average power consumption is 435 $\mu \text{W}$ . It occupies a silicon area of just 43 $\mu \text{m} \times 86~\mu \text{m}$ .