PURPOSE:To ensure the perfect compensation for the variation of amplitude caused, if any, by the variation of the input frequency in the differentiating (integrating) circuit, by giving the control to the multiplying action of the multiplication-type D/A converter according to the deviation between the input and output signals. CONSTITUTION:With application of input signal Vin, the signal received the 90- degree phase shift at differentiating (integrating) circuit P is applied to multiplication-type D/A converter D/A. Then output signal Vout received the adjustment of amplitude at converter D/A is delivered. On the other hand, signals Vin and Vout are applied to comparator D. And comparator D actuates oscillator OSC to apply the pulse to reversible counter U/D as well as to make counter U/D perform the up- or down-counting in accordance with the comparison result of the two input signals. As a result, the output of counter U/D rises up or lowers down, and converter D/A increases or decreases the amplitude of signal Vout in proportion to the ascent or descent of the output of converter D/A. Thus the control is given to always secure the constant amplitude of signal Vout.
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