| 摘要 |
1,061,133. Filter circuits employing transistors. G. M. FERRIEU. April 7, 1965 [April 8, 1964], No. 14675/65. Heading H3T. An electrical network comprises an unbalanced filter metwork 10 and a high gain amplifier 11; the filter terminals 102, 104 are respectively connected to the amplifier input and output terminals 112, 114, as a consequence of which the effective impedance across a first terminal 111 common to the input and output circuits of the amplifier and a second terminal 101 common to the input and output circuits of the filter is substantially equal to the transfer impedance of the filter network. When used as as a filter, the arrangement is connected in parallel with a resistive load 4(R) which is driven from source 5(E) having internal impedance 6(r). The filter 10 may be of low-pass, high-pass or band-pass type (Figs. 3-9, not shown), or a band-pass filter may be obtained by cascading low- and high-pass filters (Fig. 11, not shown); it possesses the advantage that in the low-pass form low frequencies, and particularly D.C. do not have to pass through the amplifier. |
