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Current Switch Circuit With VPNP Pull-Up And Load Device

IP.com Disclosure Number: IPCOM000102825D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Related People

Smith, GE, III: AUTHOR [+2]

Abstract

Circuitry modification for semiconductor devices has resulted in the addition of an active pull-up device to a standard current switch circuit which improves the output switching characteristic. A PNP transistor is used to enhance the positive transition of the output.

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This is the abbreviated version, containing approximately 100% of the total text.

Current Switch Circuit With VPNP Pull-Up And Load Device

      Circuitry modification for semiconductor devices has resulted
in the addition of an active pull-up device to a standard current
switch circuit which improves the output switching characteristic.  A
PNP transistor is used to enhance the positive transition of the
output.

      The circuit of the drawing, with the exception of transistors
TP1 and TP2, is a conventional current switch logic gate.  Additional
logic input may be added by using parallel transistors for TL with
the extra bases used as additional inputs.

      TP1 and TP2 act as switched active loads for the output with TL
and TR providing an active pull-down for the output and its
complement, respectively.  TP2 will pull the output up when the
complement output is low since it will have a sufficient Vbe to turn
it on; TP1 will pull the complement output up when the output is low
since it will have a sufficient Vbe.

      In implementing the development, since speed is important, the
2 PNP transistors should be fast devices. The devices should have
good saturation recovery time.  The signal swing is automatically
clamped at Vbe (pnp) - Vce, sat. Fan-in may be extended as needed and
power dissipation may be reduced relative to the standard current
switch emitter-follower (CSEF) circuit since the emitter followers
have been eliminated.

      Disclosed anonymously.