| 摘要 |
PURPOSE:To enable the base current of a bipolar transistor to be externally controlled by a method wherein a digital circuit is composed of a MOS transistor and a bipolar transistor, where a circuit which controls the base current of the bipolar transistor is included in the digital circuit concerned. CONSTITUTION:N-type MOS transistors 33 and 34 are connected to the base electrodes of NPN type bipolar transistors 35 and 36, which constitute a totem pole output buffer, to control a base current, and the gate electrodes of the MOS transistors 33 and 34 are extended outside as current control terminals 20. When a voltage VDD is applied to an input terminal 10, a P-type MOS transistor 30 is turned OFF and N-type MOS transistors 31 and 32 are turned ON. A current flowing through the base electrode of the NPN type bipolar transistor 36 is determined depending on the ratio of a resistor 40 to the ON-resistance of the N-type MOS transistor 34. The ON-resistance of the N-type MOS transistor 34 can be varied by a voltage applied to the current control terminals 20, so that the base current of the NPN type bipolar transistor 36 can be controlled. |
