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High Bandwidth Multiple Threshold Level Detector for Redundant Signal Detection

IP.com Disclosure Number: IPCOM000113688D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Baumgartner, SJ: AUTHOR [+3]

Abstract

A high bandwidth, redundant level detector circuit is disclosed. The differential ECL circuit, which is designed in a high speed bipolar technology, performs redundant level detection on an incoming serial data stream while using no external components. It also has the flexibility to be set at different level detection thresholds. An ideal application for this invention is for signal detection in an optical communications network which requires redundancy to meet international laser safety standards.

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High Bandwidth Multiple Threshold Level Detector for Redundant Signal
Detection

      A high bandwidth, redundant level detector circuit is
disclosed.  The differential ECL circuit, which is designed in a high
speed bipolar technology, performs redundant level detection on an
incoming serial data stream while using no external components.  It
also has the flexibility to be set at different level detection
thresholds.  An ideal application for this invention is for signal
detection in an optical communications network which requires
redundancy to meet international laser safety standards.

      In Fig. 1, a circuit schematic of a 1/2 wave rectifier is
shown.  This circuit performs the level detection of the differential
signal present at the C0 and C1 inputs.  Q0-Q4 and R0-R4 comprise a
linear diff amp that has a resistor mismatch between R1 and R2.  This
induces an offset in the output of the diff amp which is amplified
even more by the next diff amp, Q8-Q10 and R7-R9.  When the input
signal amplitude is high enough to overcome the offset in the first
diff amp, node 6 swings above and below node 7 which is a DC
reference.  Q12 pulls node 8 above node 9 when node 6 goes high and
outputs 10 and 11 indicate a low output or signal present.  When the
signal is too low to overcome the offset in the first diff amp, the
second diff amp never switches enough for node 6 to go above node 7.
When node 6 goes low, it must stay low long enough for the trickle
current so...