LOGARITHMIC_LIGHT_METER_CIRCUIT

Published:2009/6/25 2:22:00 Author:May | From:SeekIC

The meter reading is directly proportional to the logarithm of the input light power. The logarithmic circuit behavior arises from the nonlineardiode pnjunction current/voltage relationship. The diode in the amplifier output prevents output voltage from becoming nega-tive (thereby pegging the meter), which may happen at low lightlevels due to amplifier bias currents. R1 adjusts the meter full-scale deflection, enabling the meter to be calibrated.



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