0_100°F_GIVES_0_1_kHz_OUTPUT

Published:2009/7/8 5:04:00 Author:May | From:SeekIC

Circuit provides direct temperature-to-frequ ency conver-sion at low cost for applications where digital output is desked. Temperature sensor is 1N4148 diode having -2.2 mV/°C temperature shift, controlling AD301 opamp in relaxation oscillator drcuit. Compensated 1N821 zener stabilizes against supply changes. Output network using 680 pF and 2.2K differentiates 400-ns reset edge of negative-going output ramp of opamp and drives single-transistor inverter to provide TTL output. Accuracy is within 0.3°F.-J. Williams, Designer's Guide to: Temperature Measurement, EDN Magazine, May 20, 1977, p 71-77.



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