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Temperature Independent Photosense Amplifier

IP.com Disclosure Number: IPCOM000097374D
Original Publication Date: 1962-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Bellamy, PD: AUTHOR [+3]

Abstract

This one shot circuit is relatively in sensitive to input bias level changes. These bias changes can be caused by a change of resistance of photosensitive element PC due to temperature variations.

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Temperature Independent Photosense Amplifier

This one shot circuit is relatively in sensitive to input bias level changes. These bias changes can be caused by a change of resistance of photosensitive element PC due to temperature variations.

In the quiescent state, transistors T1 and T2 have the same base potential. Because the emitter of T1 is more negative than the emitter of T2, due to the voltage drop across diode D and resistor R2, T1 is biased off while T2 is conductive. Regardless of variations in the input bias level, the base potentials of T1 and T2 always remain substantially identical and, in the absence of an input pulse, act to continually maintain T1 and T2 in their stable, quiescent states.

If PC is suddenly rendered conductive by a ray of light, a negative input pulse is simultaneously applied to the base of T1 and delay network D1. The input pulse renders T1 conductive, causing its emitter potential to fall. This decrease is reflected to the emitter of T2 and causes it to cease conduction. The collector potential of T2 rises and produces an output. When the leading edge of the negative input pulse passes through network D1 and appears at the base of T2, conduction is re-initiated in it, causing termination of the output and resetting the circuit to its quiescent state.

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