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Bipolar Driver for Interfacing Bipolar and FET Circuits

IP.com Disclosure Number: IPCOM000077062D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hansen, AA: AUTHOR [+2]

Abstract

The high-speed, low-standby power circuit shown in the drawing converts bipolar transistor voltage levels to field-effect transistor (FST) voltage levels. Operational power is used only during transition when circuit selection is made. Of the seven transistors in the interface driver, only two conduct in the standby (unselected) condition if a constant current source is used. Only one transistor conducts during standby if a pulsed power current source is substituted.

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Bipolar Driver for Interfacing Bipolar and FET Circuits

The high-speed, low-standby power circuit shown in the drawing converts bipolar transistor voltage levels to field-effect transistor (FST) voltage levels. Operational power is used only during transition when circuit selection is made. Of the seven transistors in the interface driver, only two conduct in the standby (unselected) condition if a constant current source is used. Only one transistor conducts during standby if a pulsed power current source is substituted.

Current switch T1, T2 changes state during selections such that T1 turns on and T2 turns off. The collector current of T1 is supplied through the resistor Rc which causes a voltage drop across the emitter-base junction of T3, turning on T3 and applying base drive for T4. T3 and T4 form an SCR which latches during the transient time. The SCR supplies a substantial amount of base current drive for turning T5 on. T5, in turn, provides the current for charging the load capacitance CL which may be of the order of hundreds of picofarads.

As the output voltage rises, the base voltage of T5 follows the output voltage, tending to turn the SCR off. When the base of T5 reaches 5 volts, for example, the SCR is off but the base voltage at T5 continues to rise due to coupling effects, holding T5 on. T5 is turned off when the output voltage reaches a potential equal to the difference between V and Vce of T5. This is the selected state and power is dissipated f...