| 摘要 |
PURPOSE:To obtain two kinds of characteristics by one filter by obtaining characteristics reciprocal to filter characteristics by supplying the output of the filter to a differential amplifier. CONSTITUTION:An input signal to and output signal from low-pass filter LPF are supplied to differential amplifier A. Between the input and output signals of LPF, there is a difference equivalent to the decrement of the output signal. Therefore, differential amplifier A generates an output signal of high-pass filter characteristics. Thus, an output signal of low-pass filter characteristics appears at terminal O1, and the output signal of high-pass filter characteristics at terminal O2. When this circuit is applied to a noise eliminating circuit, the input signal to LPF has only the signal component passed through LPF and appearing at terminal O1 and the noise component appears at terminal O2. Thus, a signal for cutting a noise can easily be obtained at terminal O2. |
