| 摘要 |
PURPOSE:To stabilize the operation of an output transistor TR in a short time for an audio power amplifier, by providing a constant voltage bias circuit with a means to increase the bias current of the output TR via a driving TR for a fixed period after application of a power supply. CONSTITUTION:A resistor 17 is connected, when necessary, in parallel to a resistor 9 of a constant voltage bias circuit. In other words, the resistor 17 is connected after a switch 16 is closed for a fixed period after application of a power supply. Therefore the bias voltage which is supplied to the constant voltage bias circuit increases compared with a case where the switch 16 is open. As a result, a large bias current flows to output TR1 and TR2 respectively while the switch 16 is closed. Therefore the TR1 and TR2 generate the heat at an early time. That is, it is possible to increase the bias current of the output TR for a fixed period after application of a power supply, and therefore the output TR generates the heat early. Thus the bias current is fixed in a short time to stabilize the operation of the output TR. |
