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Hysteresis Buffer for Differential Signals

IP.com Disclosure Number: IPCOM000099718D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 73K

Publishing Venue

IBM

Related People

Ippolito, PM: AUTHOR

Abstract

The circuit described in this article functions as a differential buffer which switches only after preset differential input signal thresholds have been exceeded. It has particular application to fiber-optics receivers and differential line receivers.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Hysteresis Buffer for Differential Signals

       The circuit described in this article functions as a
differential buffer which switches only after preset differential
input signal thresholds have been exceeded.  It has particular
application to fiber-optics receivers and differential line
receivers.

      The circuit shown in Fig. 1 functions as a fully differential
hysteresis buffer, one which does not switch until the input signal
exceeds a preset differential threshold value.  As such, this buffer
is valuable for applications in which there is appreciable noise on
the input signal, noise which must be rejected to prevent false
switching.

      In the Fig. 1 circuit, transistors T1, T2, T3 and T4 are
arranged in a standard latch configuration, with transistors T5 and
T6 comprising input transistors for the latch.  The circuit remains
latched in a first state until the magnitude of the differential
input signals V1 and V2 is sufficient to cause the latch to switch.
This switching level is programmable, as determined by the ratios of
resistors R1/R2 and R3/R4.  The ratio of resistor values R1/R2 is
selected such that the magnitude of the input signal to T5 must
exceed a predetermined up-level value to effect switching of the
latch.  The ratio of resistor values for R3/R4 is likewise selected
relative to the up-level of the input signal to T6.  With the
resistor value ratios thus appropriately established, the switching
levels can be selected to reject...