| 摘要 |
An output amplifier comprises an output transistor and a biasing transistor whose emitter is connected to the emitter of the output transistor. The polarity of the biasing transistor is the same as that of the output transistor. Resistors of small resistance are connected to the collector and base of the biasing transistor, respectively. The other ends of these resistors are connected to the base of the output transistor. When an input signal in the positive cycle is applied to the base of the output transistor, the circuit comprising the biasing transistor and the resistors operates as a resistance circuit. On the other hand, when no signal is applied to the base of the output transistor, or when a signal in the negative cycle is applied to the base of the output transistor, the circuit operates as a current mirror circuit. Therefore, when the output transistor is cut off, the biasing transistor is simultaneously cut off.
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