| 摘要 |
A circuit for selectively combining an input signal with a selected fraction of the input signal, twice differentiated, is comprised of two amplifier circuits, each having two input stages and a dual output stage with one output stage of each amplifier circuit being gain controllable in response to a control signal. One of the gain controllable output stages of one amplifier and the non-gain controlled output stage of the other amplifier are connected to a single combined output terminal. The other output stages are connected to a circuit ground. An input signal is supplied to one input stage of each amplifier circuit and the same input signal, after being double differentiated by means of an inductor and capacitor, is supplied in noninverted form to the other input stage of one of the amplifier circuits and is supplied in inverted form to the other input stage of the other amplifier circuit. By a suitable choice of a control signal to the gain controllable output stages, the signal appearing at the output terminal will be some fraction of the double differentiated input signal either added to or subtracted from the input signal.
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