Tunable Square-Wave Generator for Integrated Sensor Applications

An Operational Transconductance Amplifier (OTA) based square-wave and clock generator with independent control over amplitude and frequency has been presented in this paper. Two out of phase square-waves along with rail to rail clocks are generated which are suitable for integrated sensor applications. Both amplitude and frequency of the waveform generator can be controlled independently by tuning the bias currents of the OTAs. These bias currents are controlled by two highly linear tuning OTAs. The complete circuit is implemented fully on-chip in UMC 0.18 μm CMOS process technology making it possible for integration with micro-sensing devices. The measured results show wide sweep capability of amplitude from 280 mVpp to 1 Vpp and frequency from 120 kHz to 900 kHz approximately with good linearity. This generator is suitable for integrated capacitive and resistive sensors and other instrumentation applications.