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Browse Prior Art Database

Automatic Gain Control

IP.com Disclosure Number: IPCOM000097114D
Original Publication Date: 1962-May-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Hardin, WW: AUTHOR

Abstract

The arrangement provides automatic feedback control of the gain of a photomultiplier. The latter employs a plurality of dynode elements energized at increasingly higher potentials. Photomultiplier PM has a cathode connected to a high voltage source -HV. PM also has a plurality of dynodes D1...D9 and D1O. A resistance network is connected between -HV and ground. Such provides an increasing potential for each of the dynodes D1...D10.

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Automatic Gain Control

The arrangement provides automatic feedback control of the gain of a photomultiplier. The latter employs a plurality of dynode elements energized at increasingly higher potentials. Photomultiplier PM has a cathode connected to a high voltage source -HV. PM also has a plurality of dynodes D1...D9 and D1O. A resistance network is connected between -HV and ground. Such provides an increasing potential for each of the dynodes D1...D10.

The PM anode connects to a transistor amplifier including transistor TR1, biasing resistors R1 and R2, and output resistor R3.

The negative peaks are indicated by the charge on capacitor C1, diode Da being utilized to exclude positive changes in potential. C1 and adjustable voltage divider R4 supply the peak negative potentials to a transistor amplifier including transistor TR2. The output voltage developed across resistor R5 is fed to the base of transistor TR3 whose output connects to the PM dynode D10.

If the PM output signal is too large, a negative voltage is fed back through the transistor TR3. Such action controls the D10 voltage, causing the voltage to be reduced and thus reducing the PM gain. Conversely, a signal which is too small causes the PM gain to be increased. Although the connection to PM from TR3 is to D10, the remaining dynodes are affected, to a certain degree, by the variations in the feedback voltage supplied to D10.

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