| 摘要 |
PURPOSE:To improve the separation characteristic and to decrease the leak of a control pulse to a signal system by connecting two resistors and two transistors (TRs) poled oppositely to a signal line so as to interrupt an input signal from being outputted to the output. CONSTITUTION:The resistors R1, R2 are connected in series to the signal line and the TRs 13, 14 poled oppositely are further connected thereto. When a control pulse A applied in synchronizing with L/R channel audio signals included in the output of a D/A converter 10 goes to ''H'', the TR13 is turned on and the signal is attenuated. Further, the TR14 is turned on through the inversion of the pulse A so as to attenuate the signal. Then the degradation in the separation characteristic is prevented. When the pulse A goes to ''L'' next, an output signal of the converter 10 is outputted as it is as the L channel signal. In this case, when the pulse A shown in Fig. (a) is applied to the TR13 and its inverted pulse A' (shown in Fig. c) is applied to the TR14, noises shown in Figs. b, d are leaked to the signal system at its leading. Since the polarity of both noise signals is opposite and the signals are produced almost at the same time in this case, the result is negligibly small as shown in Fig. (e). |
