An asymmetric MOSFET-C band-pass filter with on-chip charge pump auto-tuning

Abstract

An asymmetric MOSFET-C band-pass filter (BPF) with on chip charge pump auto-tuning is presented. It is implemented in UMC (United Manufacturing Corporation) 0.18 μm CMOS process technology. The filter system with auto-tuning uses a master-slave technique for continuous tuning in which the charge pump outputs 2.663 V, much higher than the power supply voltage, to improve the linearity of the filter. The main filter with third order low-pass and second order high-pass properties is an asymmetric band-pass filter with bandwidth of 2.730–5.340 MHz. The in-band third order harmonic input intercept point (IIP3) is 16.621 dBm, with 50 Ω as the source impedance. The input referred noise is about 47.455 μVrms. The main filter dissipates 3.528 mW while the auto-tuning system dissipates 2.412 mW from a 1.8 V power supply. The filter with the auto-tuning system occupies 0.592 mm2 and it can be utilized in GPS (global positioning system) and Bluetooth systems.

Design of Low Power and High Linearity Gm-C Low Pass Filters

“…Active-RC filter [2] has better linearity and larger dynamic range than others, but it requires the operational amplifier's bandwidth is larger, which will increase the power consumption of the circuit, and it cannot precisely adjust the frequency characteristics by the capacitance switch or resistance, which limits its application. MOSFET-C filter [3] is use the MOSFET resistor that work in the triode region instead of resistance, it is an extension of active RC, at the expense of the linearity and dynamic range cost to achieve precise adjustment of the frequency characteristics, and has a serious distortion, power consumption, that is also equal to active RC. The Gm-C filter [4] using OTA as active elements without low impedance output stage, the designed filter's bandwidth can reach the unity gain bandwidth and frequency can be continuously adjusted, the power required is minimal.…”