| 摘要 |
A limit is placed upon the maximum collector current available from a common-emitter transistor in the driver stage of an amplifier provided with overall feedback from its output stage following the driver stage to its input stage preceding the driver stage. This limit is imposed by saturation of a transistor in the input stage, which is of complementary conductivity type to the common-emitter transistor and which applies its collector current as base current to the common-emitter transistor, limiting the voltage applied to its base circuit. The common-emitter transistor in the driver stage is provided with emitter degeneration resistance, so limiting the voltage applied to its base circuit results in limiting the drive capability of the driver stage. This prevents the overall feedback increasing the output current of the driver stage so much it interferes with restriction of the base-current drive whenever a tendency towards overly large current flow through the output transistor is sensed. This forestalls increased dissipation in the output transistor that might damage or destroy it. |
