| 摘要 |
<p>1,119,509. Transistor amplifiers. INTERNATIONAL STANDARD ELECTRIC CORP. 23 June, 1967 [30 June, 1966], No. 29111/67. Heading H3T. A filter, as shown a low-pass filter, comprises an active filter 1 followed by a parallel-T null network 2 and by an impedance matching circuit 3, the active filter comprising a filter (low-pass) composed of two resistors R 1 , R 2 and two capacitors C 1 , C 2 followed by a feedback D-C amplifier 4. In the low-pass filter shown, capacitor C 1 is connected to the output of the amplifier. Resistors R 1 and R 2 may be interchanged with capacitors C 1 , C 2 to form a high-pass filter (Fig. 3, not shown). The response curves of active filter 1 and network 2 combine to form a sharp cut-off for the low- or high-pass filter as applicable. Amplifier 4 comprises a differential amplifier composed of a long-tailed pair, signal input E 1 being applied to one input and the feedback E 2 to the other, followed by a three-stage amplifier comprising two emitter-follower stages and an intermediate common emitter stage in cascade (Fig. 5, not shown).</p> |
