ACCURATE_LOG_AMPLIFIER

Published:2009/7/13 1:54:00 Author:May | From:SeekIC

The log circuit consists of an instrumentation amp and an Op amp together with a diode-connectedtransistor that produces a voltage proportional to the logarithm of the current A circuit consisting of avoltage reference, an instrumentation amp,and an op amp,togetherwith a diode-connected transistor,acts as a reference circuit. A thermometer IC,a fixed-gain instrumentation amp,and a divider circuitprovide the necessary temperature compensation and scaling for a transfer function∶Vout51.985 log10 (Vin/1V)Vref must be set to 1.000 V and, with Vin 5Vref, the gain adjust has to be set so that VO 50 V. Calirelbration low input voltage is done by changing buffer A4's offset voltage.



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