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Push Pull Driver with High Uplevel Output Voltage

IP.com Disclosure Number: IPCOM000044804D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Mullgrav, AL: AUTHOR

Abstract

This totem pole push-pull driver circuit includes a Schottky- clamped transistor T2 having a base resistor R2. Sufficient base current is provided through resistor R2 to keep the Schottky diode forward biased at all times. The resulting VCE of transistor T2 raises the emitter voltage of T1 by about .25V, increasing the Down level noise tolerance at input A.

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Push Pull Driver with High Uplevel Output Voltage

This totem pole push-pull driver circuit includes a Schottky- clamped transistor T2 having a base resistor R2. Sufficient base current is provided through resistor R2 to keep the Schottky diode forward biased at all times. The resulting VCE of transistor T2 raises the emitter voltage of T1 by about .25V, increasing the Down level noise tolerance at input A.

The additional emitter voltage of T1 enables that transistor to be turned off completely when the input is at a Down level, even though that Down level might be slightly above ground. With T1 fully off, there is no collector current being drawn through R1, and thus the output voltage at node 10 is higher. The value of R1 may now be increased to slow down the output transitions, if desired, without significantly lowering the least positive Up level, since R1 now only carries T3 base current when T1 is off.

The VCE of T2 is sufficiently smaller than that of T4 so that T3 can always be turned off when T1 and T5 are on.

Disclosed anonymously

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