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Latching Threshold Detector

IP.com Disclosure Number: IPCOM000097809D
Original Publication Date: 1961-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Brown, DP: AUTHOR [+2]

Abstract

The threshold detector latches up when the threshold of the circuit is reached or exceeded.

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Latching Threshold Detector

The threshold detector latches up when the threshold of the circuit is reached or exceeded.

An input signal 1 and a G1 signal are applied to a negative AND circuit 2 whose output is connected to the base of transistor T1. Transistor T1 is coupled to a transistor T2 and a G2 signal is applied to the base of T2. The output is supplied by the collector of T2. Transistor T1 is normally off, T2 is normally on, the G1 and input 1 signals are normally at their up level, and G2 is normally at its down level.

If the input 1 goes down to or below the threshold of the circuit when G1 is at its negative down level, T1 attempts to turn on. If G2 goes up when the input is at or below its threshold and G1 is down, T2 attempts to turn off. This action is regenerative until T1 is on and T2 is off, the output going negative to indicate that the threshold is exceeded. After the regeneration is completed, the G1 signal is returned to its up level so that no input signal other than the sampled one is detected. The output voltage remains negative as long as G2 is at its up level. Upon the return of G2 to its down level, T2 turns on and the regenerative loop turns T1 off.

Choose V2> E> V1, V3. When T2 is on, emitter current is supplied by diode D2 and also diode D1 through R1. The emitter of T1 is approximately at E assuming that D1 and D2 are the same type diodes. As T1 attempts to turn on, it draws current through R1, thus reduces the current supplied to T...