| 摘要 |
PURPOSE:To improve the dielectric strength by providing a level shift circuit keeping a collector-emitter voltage of a transistor (TR) constant and a bias circuit keeping the operating range of the TR active. CONSTITUTION:TRs T16, T17 and a constant power supply W2 constitute a bias circuit to TRs T14, T15 and both the TRs T14, T15 are kept to an active region. Furthermore, a minute current flowing from a power terminal V1 to a power terminal V2 through the TRT15, diodes Z1-Z3, and the TRT16 pushes up the emitter potential of the TRT15 by a voltage drop of the diodes Z1-Z3 to a base potential of the TRT14. Since the resistance value of a resistor R5 is small, the collector-emitter voltage of an output TRT13 is limited nearly to the voltage drop of the diodes Z1-Z3. That is, the dielectric strength of the operational amplifier is boosted by limiting the maximum collector-emitter voltage loaded by the TRT13 by means of said boostrap circuit.
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