An Ultra-Low Power Low Phase Noise Pseudoresistive Astable Multivibrator for MICS Band Wireless Sensor Node Applications

The paper presents the design of an ultra-low power pseudoresistive astable multivibrator for Medical Implant Communications Service (MICS) band applications. Instead of tail current source, we have used a MOSFET operating in deep triode region (acting as pseudoresistor) which reduces the 1/f3 noise corner of the phase noise spectrum. Complementary MOSFETs have been used as switches for linearization of its output resistance which reduces the phase noise further. A resistor based tuning circuit provides bias to the pseudoresistor which can be used for changing the frequency. The outputs are pseudodifferential (accomplished by two cross-coupled low strength CMOS inverters) providing rejection to common-mode noise. The entire circuit has been designed and simulated in Cadence Virtuoso using gpdk180 nm technology library and draws a current of 150µA from 1.8V power supply while achieving a phase noise of −100dBc/Hz @ 1 MHz offset. Such low phase noise performance at this ultra-low power has not been seen in other MICS band oscillators so far.