| 摘要 |
The present invention provides a switching circuit comprising a current detecting circuit that detects current waveform of a main switch in real time waveform and outputs it in low impedance. The switching circuit comprises the current detecting circuit having the main switch ( 11 ), of which on-voltage shows resistance characteristics, wherein a gate terminal is connected to a driving circuit ( 4 ) and further either terminal of drain or source thereof is connected to a fixed potential ( 3 ) and the other terminal thereof is connected to a load circuit ( 2 ) respectively, a first resistance element ( 21 ), of which resistance value is higher than on-resistance of the main switch connected to the fixed potential ( 3 ), a subsidiary switch ( 12 ), a source terminal thereof is connected to the first resistance element ( 21 ), an amplifier ( 6 ) that amplifies comparatively voltage generated in the first resistance element ( 21 ) and outputs to a gate terminal of the subsidiary switch ( 12 ) and the second resistance element ( 22 ) that generates voltage by amplifying on-current of the main switch ( 11 ) by connecting to the drain terminal of the subsidiary switch ( 11 ).
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