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Positive, Negative and Floating Input Voltage Level Detector With Testing Features

IP.com Disclosure Number: IPCOM000060498D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Bonnet, Y: AUTHOR

Abstract

This dual and floating detector (Fig. 1) includes a voltage comparator and positive and negative power supplies. The comparator inputs are pre-biased in differential mode by means of a dual reference source (Ref -+) and three resistors : Rdiff, R.Refand R.Ref-. When the differential floating voltage to be detected is applied to its inputs, the prebiasing differential voltage is progressively canceled and then reversed, thus turning the voltage comparator to switch and drive its output load accordingly. The reference voltage circuit (Fig. 2) includes three items: a switchable positive or negative voltage generator using one operational amplifier (OPAMP1); one non-inverting amplifier (OPAMP2); and one inverting amplifier (OPAMP3).

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Positive, Negative and Floating Input Voltage Level Detector With Testing Features

This dual and floating detector (Fig. 1) includes a voltage comparator and positive and negative power supplies. The comparator inputs are pre-biased in differential mode by means of a dual reference source (Ref -+) and three resistors : Rdiff, R.Refand R.Ref-. When the differential floating voltage to be detected is applied to its inputs, the prebiasing differential voltage is progressively canceled and then reversed, thus turning the voltage comparator to switch and drive its output load accordingly. The reference voltage circuit (Fig. 2) includes three items: a switchable positive or negative voltage generator using one operational amplifier (OPAMP1); one non-inverting amplifier (OPAMP2); and one inverting amplifier (OPAMP3). In operation, when a high level is at the (+) input of OPAMP1, its output is set to high level saturation, due to appropriate positive biasing applied to its inverting (-) input, and its open-loop configuration. Diode DD is thus conducting and exhibits a positive voltage at terminal A. This voltage provides a -Ref voltage at the output of OPAMP3. The same voltage reference circuit may be used for biasing separate detectors. A very convenient testing facility is made available to all these detectors, by swapping the polarities of Ref+ and Ref-, which turns all detectors at the same time. This swapping is fairly easily operated by simply connecting the TEST C...