| 摘要 |
The invention relates to telephone band low-pass filters for use in demodulating PCM. Such filters are formed by two sections (1, 2) connected in cascade, each section including an operational amplifier (A1, A2). A first section is of the low-pass type whose loss at high frequencies is at least 6dB/octave; the second section is a second order asymmetrical notch network with a Cauer response characteristic: the second section may comprise, for example, a double tapped bridge and an operational amplifier. <IMAGE> |
