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Preamplifier

IP.com Disclosure Number: IPCOM000095843D
Original Publication Date: 1964-Aug-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Wagner, AH: AUTHOR

Abstract

Circuit 10 functions to amplify and frequency limit a signal from magnetic head 15. Head 15 which generates a signal in response to sensing characters printed with magnetic ink, is center-tapped and connected differentially in order to reduce noise.

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Preamplifier

Circuit 10 functions to amplify and frequency limit a signal from magnetic head 15. Head 15 which generates a signal in response to sensing characters printed with magnetic ink, is center-tapped and connected differentially in order to reduce noise.

Amplifier 12 is a common emitter type with series feedback through emitter resistor 1 1. The operating point of 12 is determined by the voltage divider formed by resistors 13 and 14. Voltage gain is determined primarily by collector load impedance and un-bypassed resistor 11. The DC current in the collector circuit is determined by resistors 11 and 16.

High frequency noise is reduced by filter networks consisting of the input impedance and capacitors 17 as one filter and collector impedance and capacitor 18 as another.

In order to reduce common mode noise, resistor 19 is used in the feedback path. The value of resistor 19 is determined by the signal-to-noise ratio desired.

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