The AD590 is a 2-terminal integrated circuit temperature transducerthat produces an output current proportional to absolutetemperature. For supply voltages between 4 V and 30 V, the deviceacts as a high impedance, constant current regulator passing1 μA/K. Laser trimming of the chip’s thin-film resistors is usedto calibrate the device to 298.2 μA output at 298.2 K (25°C).The AD590 should be used in any temperature-sensingapplication below 150°C in which conventional electricaltemperature sensors are currently employed. The inherentlow cost of a monolithic integrated circuit combined with theelimination of support circuitry makes the AD590 an attractivealternative for many temperature measurement situations.Linearization circuitry, precision voltage amplifiers, resistancemeasuring circuitry, and cold junction compensation are notneeded in applying the AD590.In addition to temperature measurement, applications includetemperature compensation or correction of discrete components,biasing proportional to absolute temperature, flow rate measurement,level detection of fluids and anemometry. The AD590 isavailable in die form, making it suitable for hybrid circuits andfast temperature measurements in protected environments.The AD590 is particularly useful in remote sensing applications.The device is insensitive to voltage drops over long lines due toits high impedance current output. Any well-insulated twistedpair is sufficient for operation at hundreds of feet from thereceiving circuitry. The output characteristics also make theAD590 easy to multiplex: the current can be switched by aCMOS multiplexer, or the supply voltage can be switched by alogic gate output.