of the values of resistor 10 to resistor 12 resistor 10 resistor 12 is made equal to the nominal duty factor of the applied pulse train the positive and negative excursions of the waveform of fig2 are made equal this is the condition for maximum sensitivity note that in selecting the value for resistor 10 allowance should be made for source resistance and diode resistance that is resistor 10 should be decreased in value by an amount equal to the source resistance and the resistance of diode 16 the attenuation factor of this circuit is 0 25 that is a one percent 1 change in duty factor will produce an output voltage change that is one quarter percent 0 25 of the input voltage but it is one half percent 0 5 of the average output voltage using the example set forth earlier the output change would be ten millivolts instead of forty microvolts resistor 14 and capacitor 20 provide a ripple filter to eliminate all but the average d c level 28 which will vary in proportion to change in pulse width for some applications this ripple filter can be deleted since certain circuits will provide their own lowpass filtering function for example if point 22 was connected to a meter fig3 and 4.