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True/Complement Driver Circuit

IP.com Disclosure Number: IPCOM000089092D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Knepper, RW: AUTHOR

Abstract

This circuit combines high drive capability and a high current sinking capability in a true/complement (totem pole) current switch driver.

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True/Complement Driver Circuit

This circuit combines high drive capability and a high current sinking capability in a true/complement (totem pole) current switch driver.

The circuit essentially comprises two input level shifters (transistors T1 and T2 and resistors R3, R4, R5, and R6), one current switch (devices T3, T4, T5, T6, T7, T8, and T14, and resistors R1, R2, R7, R8, and R11) and two push-pull output sections (devices T9, T10, T11, and T12). Devices T11 and T12 have integrated within them large Schottky barrier diodes S1 and S2, respectively, in their customary and well-known manner. Device T13 and resistors R9 and R10 comprise a simple level generator current mirror circuit that generates the base voltage for device T14. Devices T3 and T4 are dual emitter/dual base devices within a single subcollector bed. Devices T1, T2, T7 and T8 are all built within a single subcollector bed. Devices T7 and T8 are transistors operated as diodes.

The operation is best understood by utilizing exemplary voltage levels to generate exemplary output signals in response to the specified input signals, although those skilled will readily adapt this circuit to other voltage levels. Assume therefore that +V is at approximately 1.4 volts. As the input signal rises from -0.4 volt to +0.4 volt, transistor T2, which is connected as a simple emitter follower, shifts this level downward by one base-to-emitter voltage drop. The resistor divider network including resistors R5 and R6 shifts this level downward even further so that a swing of -1.5 to -1.1 volts (at node 4) is applied to the base of transistor T6. Likewise, transistor T1, resistor R3 and resistor R4 shift the reference level at node 2 from ground potential downward to -1.3 volts. Transistors T1 and T2 are constructed to be identical, as are resistors R3 and R5, as well as resistors R4 and R6, thereby providing tracking between the level on node 2 and the swing on node 4.

Initially, the current (Ic) is channeled through device T5 and is...