Design and Realization of Relaxation Oscillator Circuit for Capacitive Sensor Interfacing

This work introduces a relaxation oscillator circuit for generating square waves using an active block referred to as the extra-X second-generation current conveyor (EXCCII). The design utilizes a single EXCCII, three resistors, and a single grounded capacitor. The used capacitor is grounded, which aids in parasitic absorption within the circuit. The circuit is designed to provide three simultaneous square wave outputs. The paper provides a comprehensive circuit investigation, covering the thorough ideal, non-ideal and parasitic conditions. To validate the suggested relaxation oscillator’s theoretical concepts, post-layout results with 180-nm generic process design kits (GPDK) technology carried out via Cadence Virtuoso are included. The used active element, EXCCII layout, measures 24 µm × 28 µm only in size. The suggested circuit achieves a high operating frequency of 10 MHz, functions on a low ±1.25 V power supply, and consumes only 0.8 mW of power. It accurately detects capacitor variations across five decades. Besides simulation results, the circuit has been experimentally validated using commercial AD844 ICs, with only two AD844 devices needed for testing.