BiCMOS switched buffers resonator for a 320 MHz 2-path sigma-delta modulator

In this paper we present a resonator circuit suitable for the implementation of high speed switched-capacitor n-path bandpass ΣΔ modulators. The resonator, implemented using a 0.8 μm SiGe BiCMOS process (f_T=35 GHz), exploits switched buffers realized using bipolar transistors to emulate the CMOS switches behavior at much higher speed. The circuit has a resonance frequency of 77.5 MHz and operates at a clock frequency of 160 MHz, consuming 120 mA from a 5 V power supply. Moreover, simulations have confirmed that with the proposed technique clock frequencies up to 200 MHz can be used without significant degradation of the performance.