| 摘要 |
PURPOSE:To provide an ideal muting with a simple circuit and to prevent the generation of switching noise by using a multi-emitter transistor (TR) for TRs of a differential pair and connecting the emitter to an output of a control circuit. CONSTITUTION:A 1st emitters of multi-emitter TRs Q1, Q2 and a collector of a TR Q4 are connected and a 2nd emitters of the TRs Q1, Q2 are connected to a 1st and a 2nd collectors of a multi-collector TR Q3 independently. Further, the TRs Q3, Q4 are of differential constitution and bases are led out as a 1st and a 2nd mute control terminals 3, 4, and bases of the TRs Q1, Q2 are led as a 1st and a 2nd input terminals 1, 2. Since the TRs Q1, Q2 are biased by a constant current from the emitter side, a strong negative feedback is applied, the amplification factor is nearly zero and ideal muting is applied. Further, no switching noise is caused.
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