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Circuit with Linearly Increasing Negative Feedback

IP.com Disclosure Number: IPCOM000073562D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 3 page(s) / 41K

Publishing Venue

IBM

Related People

Mathews, KF: AUTHOR

Abstract

This circuit consists of an emitter-coupled logic configuration with a unique type of threshold negative feedback. The feedback network uses Schottky diodes of relatively low conducting junction voltages to maintain a constant potential difference between the input voltage to the ECL circuit and the reference (threshold) voltage once a minimum up or down level has been achieved. The resulting advantages are that switching speed and noise tolerance are independent of signal swing, and are relatively insensitive to incremental changes in circuit parameters.

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Circuit with Linearly Increasing Negative Feedback

This circuit consists of an emitter-coupled logic configuration with a unique type of threshold negative feedback. The feedback network uses Schottky diodes of relatively low conducting junction voltages to maintain a constant potential difference between the input voltage to the ECL circuit and the reference (threshold) voltage once a minimum up or down level has been achieved. The resulting advantages are that switching speed and noise tolerance are independent of signal swing, and are relatively insensitive to incremental changes in circuit parameters.

Referring to drawing 1, transistor T1 and resistor R1 form a simple emitter- follower which drives a current switch configuration made up of transistors T2, T3 and R2. The emitter-follower also drives the feedback network consisting of two parallel Schottky diodes D1 and D2, each opposing the other with respect to forward current flow, and resistor R4 and capacitor C. A complementary output is shown via collector resistor R3 and emitter-follower T4. A true output, not shown, is also available from the collector of T3.

The static relationship between the voltage at A (the input to the current switch) and the voltage at B (the reference voltage of the current switch) is shown in drawing 2B. This sketch is developed by analyzing the feedback network as the input voltage passes through its normal range of values. When the input is at a quiescent down level, the voltage at A is more negative than -V1 by a potential difference which is greater than the conducting voltage (delta V) of D2. The voltage at B is therefore delta V volts more positive than at A, and will remain so until point A becomes sufficiently positive to cut D2 off. As point A continues to go even more positive, it e...