Browse Prior Art Database

Fully Compensated Reference System for Higher Performance CSEF Design

IP.com Disclosure Number: IPCOM000119336D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Leung, WC: AUTHOR

Abstract

A method is disclosed for generating the references of the current switch emitter follower (CSEF) circuit on semiconductor chips to improve its noise tolerance. The method generates a reference voltage VRX which tracks with VCC and VT, thereby enabling the VRX to track with the up levels. A VX voltage will also be generated to monitor all the CSEF down levels to track with VRX and VEE.

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Fully Compensated Reference System for Higher Performance CSEF Design

      A method is disclosed for generating the references of
the current switch emitter follower (CSEF) circuit on semiconductor
chips to improve its noise tolerance.  The method generates a
reference voltage VRX which tracks with VCC and VT, thereby enabling
the VRX to track with the up levels.  A VX voltage will also be
generated to monitor all the CSEF down levels to track with VRX and
VEE.

      In some CSEF circuits, the CSEF down level is regulated by a
VXGEN (current source reference generator), which is also a reference
for the differential current switch (DCS) current source.  The up
level is not regulated and swings with VCC and VT, the DCS is also
subject to these variations.  Large variations of source current
results from these VCC and VT changes.  Other compensation methods,
such as compensated current switch emitter follower (CCSEF), feedback
current switch emitter follower (FCSEF) and variable threshold (VTL)
make use of additional components attaching the collectors of the
current switches.  However, these can result in degraded performance
and have a density drawback because any additional components shall
increase the collector capacitance as well as the component counts on
the basic current switch circuits.

      The fully compensated reference system of Fig. 1 provides
coordinated references for CSEF's current source VX and current
switch VRX.  The VSENSE comes into play wherein a desired voltage is
regulated to VSR within the tolerance of the amplifier in the VXGEN.
In turn, the VSR tracks VCC and VT through the voltage follower in
the VRXGEN.  As a result, VX moves to maintain VSENSE equal to VSR as
it tracks VCC and VT.  This is because:
           VSR ...