| 摘要 |
PROBLEM TO BE SOLVED: To prevent an undesired current from flowing when a standby switch is OFF by providing a 2nd transistor(TR) which has a base where a 2nd power line is connected and a collector where a 1st power line is connected. SOLUTION: A transistor Tr2 has its emitter grounded and is applied with a source voltage Vcc2 at its base, so the transistor Tr2 turns ON. When the standby switch is turned off and the source voltage Vcc1 is stopped from being supplied, the base of a transistor Tr1 is virtually grounded. Then the base- emitter voltage of the Tr1 drops below 0.7 V, so the Tr1 turns OFF. Consequently, the collector of the Tr1 is placed in a high-impedance state, so current mirror circuits IM1 and IM2 are unable to operate and bias generation is completely stopped. When the Tr1 turns OFF, the current path is completely cut off and no leak current is generated.
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