VARIABLE_VOLTAGE_ATTENUATOR

Published:2009/6/18 23:28:00 Author:May | From:SeekIC

The front-end of this circuit is a bank of selectable bandpass filters. The output of the filter banks are shunted to ground via capacitor (C1) and PIN diode (D1). The PIN diode acts like an electroni-cally variable resistor. The resistance across the diode's terminals is a function of the applied bias voltage. This voltage, hence the degree of attenuation of the RE signal, is proportional to the setting of potentiometer RI. The series resistor (R2) is used to limit the current when the diode is forward biased. This step is necessary because the diode has a very low resistance when a certain rather low potential is exceeded.



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