| 摘要 |
PURPOSE:To reduce voltage drop quantity for the output voltage from a battery by using two FETs and two power sources. CONSTITUTION:In a power source switching circuit consisting of a main power source 23 and a battery 25, the gate source electrode of an N-MOSFET 21 is connected to the main power source 23 through a main power source switch 22. The gate power source of a P-MOSFET 24 is connected to the main power source 23 through the main power source switch 22 and the source electrode is connected to the battery 25. If the main power source switch 22 is set in an ON state, the MOSFET 21 becomes ON and the MOSFET 24 becomes OFF, so that the threshold voltage of the MOSFET 21 is supplied to a load 26. If the switch 22 is set in an OFF state, the main voltage VB of the battery 25 itself is supplied to the load 26 as a power source voltage VDD.
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