| 摘要 |
PURPOSE:To keep the output voltage at a low level in the case of small load resistance and at the same time to keep the output current at fixed level, by applying the discharge control to a time constant circuit when the current supplied to the load is reduced less that the prescribed threshold value. CONSTITUTION:A reference voltage source 8 and a time constant circuit are used as the input voltage sources of a voltage follower circuit consisting of an operational amplifier 1 and a transistor TR3. The time constant circuit contains a resistance 14 which decides a charging constant and a capacitor C12. The voltage 15 of the C12 is supplied to the positive phase input of the amplifier 1 via a resistance 13 which decides the discharging time constant of the C12. A switching TR9 is provided between the positive phase input of the amplifier 1 and a ground terminal for control of the charge/discharge of the time constant circuit. The ON/OFF control of the TR9 is carried out with the output of a comparator 10. The comparator 10 turns on the TR9 when the both-terminal voltage of a collector resistance 4 is higher than the reference voltage 11.
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