초록 ▼

In a peripheral driver circuit a switching output transistor is operated from digital logic control and is provided with a shut off circuit which turns the output transistor off when its collector supply current exceeds its saturation current. A controlled base drive current is generated in a circui

In a peripheral driver circuit a switching output transistor is operated from digital logic control and is provided with a shut off circuit which turns the output transistor off when its collector supply current exceeds its saturation current. A controlled base drive current is generated in a circuit that includes a scaled reference transistor that is operated at the same current density and the same collector voltage as the output transistor at its rated current. The reference transistor base current is amplified in a circuit having a current gain equal to the scaling between the reference and output transistors. Thus the base current applied to the output transistor is related to the driver rated current which ensures that saturation will occur up to at least the rated current and above which the shut off will be effective.

대표청구항 ▼

In a peripheral driver circuit which includes at least one current sink transistor having an uncommitted collector that can sink a substantial current in response to a logic operated base current and wherein said logic further responds to the voltage present on said uncommitted collector whereby sai

In a peripheral driver circuit which includes at least one current sink transistor having an uncommitted collector that can sink a substantial current in response to a logic operated base current and wherein said logic further responds to the voltage present on said uncommitted collector whereby said current sink transistor is turned off when said voltage exceeds a predetermined reference potential so that when said current sink transistor is driven from a current source that exceeds its saturation capability it is protected, the improvement comprising: a reference transistor; means for passing a reference current through said reference transistor; and means, responsive to said reference current, for developing a controlled base current drive for said current sink transistor whereby its saturation current is limited to a safe design value.