| 摘要 |
<p>PURPOSE:To decrease the power consumption of the protective circuti to secure a suitable application to the integrated circuit by constituting the circuit so that the amplifier is separated from the speaker after detecting the abnormal output DC potential and at the same time the current supply to the protective circuit is also cut off. CONSTITUTION:In case about +0.7V(-0.7V) output DC voltage is caused even after a fixed time since the power source make is given, transistor TrQ9(Q10) detects this voltage and then makes TrQ11 and Q12 conduct via TrQ20. And TrQ15 and Q16 are maintained under the cut-off state with relay Re opened. Then speakers SP1 and SP2 are separated from output middle points P1 and P2, thus giving protection to SP1 and SP2. With setting the conditions of (saturation voltage of TrQ19)<(base-emitter voltage of TrQ20+Zener voltage of Zener diode Z2), TrQ20 is cut off. And the emitter current of TrQ11 becomes zeroafter detection of the fault of the output DC level. Accordingly, the power consumption of the protective circuit can be decreased regardless of the power source.</p> |
