A Bidirectional Front-End for Discrete Resonating Transducers Based on A Non Ring Oscillator

This paper presents a novel method to transform a ring oscillator (RO) into a bidirectional front-end for discrete resonating transducers. The idea behind this method consists in taking advantage of the high parasitic capacitance of these transducers, in order to transform the positive feedback of the RO into a negative feedback loop. Thus, the circuit will be unable to oscillate and will provide the same behaviour of an amplifier. The operation of the proposed circuit has been verified by performing simulations of a three stages RO, connected to the Butterworth Van Dike model of a real transducer (MURATA MA40S4R), which is characterized by a resonant frequency of 40kHz. The whole circuit was implemented in AMS-350nm CMOS technology with a power supply of 3.3V. Simulation results show that a stable RO can be used as bidirectional front-end, characterized by a voltage gain of 49dB and an average power consumption of 1.3mW.