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Browse Prior Art Database

Superbuffer Logic Circuit With Diode for Lower Supply Voltage

IP.com Disclosure Number: IPCOM000121198D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 31K

Publishing Venue

IBM

Related People

Ainspan, HA: AUTHOR [+2]

Abstract

Disclosed is a logic circuit which uses a Schottky diode in the output buffer stage to achieve faster rise and fall times.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Superbuffer Logic Circuit With Diode for Lower Supply Voltage

      Disclosed is a logic circuit which uses a Schottky diode in the
output buffer stage to achieve faster rise and fall times.

      The figure shows an inverter using the circuit topology
disclosed.  However, the circuit topology disclosed covers logic
circuits in general, including NOR's and AND-OR-INVERT circuits with
fan-in greater than one.  FET's T1 and T2 comprise the inverting
stage, and FET's T3 and T4 comprise the buffer stage.  T5 is the
Schottky diode.  In any superbuffer logic circuit, a supply voltage
on the buffer stage which is lower than the diode clamping voltage of
the enhancement FET (EFET) provides three benefits.  First, it avoids
turn-on of the gate-source diode in the input FET of the circuit
being driven, thus reducing gate current in this FET and power
consumption in this circuit.  Second, it maintains a large Vgs on the
pullup EFET in the buffer stage when the output nears the high
voltage level (which equals the buffer voltage supply).  A large Vgs
keeps a large drain current flowing through the pullup, which causes
the output to reach its high level quickly.  Third, it provides a
faster falling transition, since the output node begins its fall from
a lower voltage than if a higher voltage supply on the buffer had
been used.

      One way to achieve this lower voltage supply is to provide a
second voltage supply to the chip, but this adds complexity to the
chip...