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Decreasing the Hysteresis in Hybrid Tunnel Diode Transistor Level Detector

IP.com Disclosure Number: IPCOM000096058D
Original Publication Date: 1964-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Comer, DT: AUTHOR

Abstract

A modification to a widely-used tunnel diode transistor level detector decreases the hysteresis or dead band region to a predictable small value. In the left-hand drawing, the addition of resistor Rx connecting anode 10 of tunnel diode 11 to collector 12 of transistor 13 diminishes the dead band any desired amount. If the value of the resistor is chosen to supply a pre-bias current to the diode, then the input need only rise a small amount to switch the transistor on. Hcwever, after the transistor is on, the current through the resistor Rx goes to zero, so that the input need only drop slightly to turn the transistor off.

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Decreasing the Hysteresis in Hybrid Tunnel Diode Transistor Level Detector

A modification to a widely-used tunnel diode transistor level detector decreases the hysteresis or dead band region to a predictable small value. In the left-hand drawing, the addition of resistor Rx connecting anode 10 of tunnel diode 11 to collector 12 of transistor 13 diminishes the dead band any desired amount. If the value of the resistor is chosen to supply a pre-bias current to the diode, then the input need only rise a small amount to switch the transistor on. Hcwever, after the transistor is on, the current through the resistor Rx goes to zero, so that the input need only drop slightly to turn the transistor off.

In cases where it is desired to make the hysteresis extremely small, the resistor Rx becomes small enough to affect the switching time of the hybrid level detector. For high-speed operation this is undesirable. In the right-hand drawing, the effect can be eliminated by splitting the hysteresis-decreasing resistor Rx and adding a small capacitor to ground to instantaneously bypass the feedback caused by Rx. This allows fast switching while the DC switch points are unaffected if C is chosen small enough to recover between on and off intervals.

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