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Low Noise Amplifier

IP.com Disclosure Number: IPCOM000084785D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Bealle, FJ: AUTHOR [+3]

Abstract

This circuit is directed to data reading apparatus or more particularly, to amplifier devices which receive, filter and amplify the electrical signals produced by light passing through translucent information media.

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Low Noise Amplifier

This circuit is directed to data reading apparatus or more particularly, to amplifier devices which receive, filter and amplify the electrical signals produced by light passing through translucent information media.

Known amplifiers of this type commonly have a fixed light-emitting diode (LED) light source and a simple double-diode comparator unit to select valid signals. However, this known apparatus was found to be inadequate for applications which require high-intensity lamps that have large output variations, and in which there was increased document noise due to unwanted spots on the translucent cards.

The present concept provides a method of reducing lamp variation by driving the lamp with the amplified feedback from a photocell PTX on which the light impinges after passing through the translucent card. The circuit also provides a method of countering document noise by the use of a single diode circuit GG and a low-pass filter.

The single diode circuit includes an RC timing circuit which recognizes only negative spikes above a specific voltage/width ratio.

Small slope spikes are ignored. Additionally, the low-pass filter uses another RC timing circuit to remove noise components above a predetermined frequency.

The figure is a schematic view of the circuit diagram. This lamp circuit works as a high-pass filter removing card background variations, aging affects, and supply variations. The diode circuit functions by attenuating high-frequen...