| 摘要 |
PURPOSE:To allow efficient operation upto low voltage by feeding a voltage boosted above power supply voltage to the emitter of a drive transistor for forming driving current of an output transistor on the power supply side. CONSTITUTION:A booster circuit 1 produces a voltage boosted above a power supply voltage Vcc using a periodic pulse signal subjected to frequency division by a frequency dividing circuit 16. The boosted voltage is fed to the emitter of a PNP drive transistor Q18 forming the driving current for an output transistor Q22 disposed on the power supply voltage Vcc side out of a pair of NPN push-pull output transistors Q22, Q23. Since emitter voltage of a drive transistor Q18 can be raised above the power supply voltage Vcc, output dynamic range can be enlarged by an amount corresponding to the base-emitter voltage of the drive transistor Q18. This constitution allows efficient operation upto low power supply voltage. |
