An integrated controller for tunnel sensors

Micromachined tunnel sensors require electronic circuitry to servo control their tunnel gap width. In this paper, we present the first integrated and complete tunnel sensor controller. This self-contained CMOS controller prov ides all necessary controller functions; it generates a tunnel junction bia s, senses the tunnel current by dropping it actress a diode-connected trans istor, compares the voltage across this diode to;In internally generated pr oportional-to-absolute-temperature reference, derives a feedback signal wit h an externally configural,le frequency response, generates a high-voltage electrostatic drive, and provides a low-voltage output for external circuit ry. If he chip requires -5 and -40-V power supplies and a compensation RC n etwork, consumes 0.9 mW power, has a power-supply rejection ratio of 30 dB, and has a total die area, exclusive of bond pads, of 0.35 mm(2), The circu it compensates for tunnel junction nonlinearity and contributes less signal noise than the sensor that it controls.