| 摘要 |
PROBLEM TO BE SOLVED: To reduce the ripple voltage in a DC voltage output from a switching power source circuit. SOLUTION: The power source circuit comprises a step-up converter 23 for inputting the voltage of a battery 25, and an amplifier circuit 24 having operational amplifiers 35, 36 operating according to its output voltage V1 as a power source voltage. A reference voltage Vr2 of a reference voltage generator 37 constituted as a band gap regulator is given to a non-inverting input terminal of the amplifier 35. An output voltage of the amplifier 35 is voltage divided by a voltage divider 38, and a predetermined divided voltage selected by switching a switch circuit 39 is fed back to the non-inverting terminal of the amplifier 35. Since the amplifiers 35, 36 have a high power removing ratio (PSRR), a ripple voltage of the output voltage V2 is suppressed. |
