SU792357A1 - Photoelectron device - Google Patents

Description

The invention relates to the field of electronics, in particular to photoelectronic devices used, for example, in optical communications equipment. A photovoltaic device for operation in optical communication lines is known in the presence of an external background illumination, which changes its value in a large dynamic range. It has a threshold comparison circuit that regulates the voltage; given to dynodes and thereby maintain the constant gain factor. A disadvantage of this device is the lack of sensitivity adjustment when operating with an increased level of background radiation. The closest technical solution to this invention is a photovoltaic device containing a photomultiplier tube, a voltage divider, the resistors of which are bridged by controllers of semiconductor elements, and a constant voltage source electrically connected to the photocathode of the photomultiplier tube and C2J diode-resistor circuits .

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The disadvantage of the known photovoltaic device is that, when working with large variations of background illumination, it does not allow recording of short-duration signal radiation due to the significant inertia of the regulating circuit. This especially affects the operation of such a device in high-speed optical links with signal durations of a few nanoseconds. In addition, fluctuations in the secondary emission coefficient of the last cascades of the PMT lead to the triggering of the regulating element, which causes a decrease in the voltage of the photocathode — the 1st dynode and, as a result, a decrease in the sensitivity of the photoelectric device. The aim of the invention is to expand the linear range of sensitivity adjustment of a photovoltaic device. The goal is achieved by the fact that in the proposed device the multiplier dinodes are connected to a voltage divider by resistors, the diodes of diode-resistor circuits are connected to the diodes, the cathodes of diodes

They are connected through capacitors. With control electrodes of controlled semiconductor elements, and the voltage divider is connected to a constant voltage source through a varistor.

In addition, in order to expand the linear sensitivity adjustment range of a photoelectric device when operating with a high background radiation level, the controlled semiconductor elements are made on thyristors.

The drawing shows a diagram of the described device.

The photoelectric device contains a photomultiplier tube 1 with dynodes 2, a voltage divider 3, controllable semiconductor elements (thyristors) 4, resistors 5, capacitors b, diodes 7, resistors 8, and varistor 9.

The resistors 8, together with the corresponding diodes 7, form threshold circuits fed from the bias source. Voltage divider 3 is connected to a power source through a varistor 9. The linear range of sensitivity adjustment of the photoelectric device is determined by the maximum permissible current of the multiplier anode, and the gain factor by the product of the gain factors at the homedressed dynode. In this case, the linearity of the output characteristics of the PMT is disturbed due to two reasons: a change in the gain of the PMT due to fluctuations of the anode feed and the operation of the photocathode under conditions of powerful light when the light characteristic of the photocathode enters the streamline mode. From the condition of linearity of the PMT gain factor, we obtain

yo t-n

where M is the gain of the PMT; 1, - cathode current. For a given value, the maximum value is determined, -y for each dynode, where and r are, respectively, the current coming to the k-th dynode, and the current ukhdchy from this dynode. If and then the thyristors 4 are locked at the control electrode due to diode-resistor circuits 7 and 8, since the potential of unlocking the thyristors 4 is selected at the level A. When d / "oh t increases the voltage drop across the resistor 5, the diode 7 opens, the potential of the control electrode of the thyristor 4 increases, the thyristor 4 opens and shunts the diode gap

(Af-to-Y). Using a varistor 9. w the voltage divider circuit 3 allows you to compensate for the change in current of the divider 3, occurring when the dynode gaps are turned off, which results in the dynod voltage being retained; Decreasing A ,, to a level lower than A-fff ax closes and the shunting resistance of the divider 3 stops.

The use of separate adjustment for the kayodoma (or several) dynoids by introducing thyristors controlled through threshold circuits allows increasing the depth of sensitivity adjustment, as well as reducing the inertia of the chain adjusters. As a result, the device’s temporal characteristics and device operation are improved.

0 exposure to powerful background light.

Claims (2)

1. A photoelectric device containing a photomultiplier tube, a voltage divider, the resistors of which are shunted by controllable semiconductor elements, and a constant voltage source electrically connected to the photomultiplier photocathode and diode-resistor circuits, characterized in that, in order to expand the linear the sensitivity adjustment range of the photovoltaic device, the multiplier dinodes are connected to the voltage divider by means of resistors, 0 anodes of diodes of diode-resistor circuits are connected to dynodes, the cathodes of diodes are connected via capacitors to control electrodes of controlled semiconductor elements, 5 and the voltage divider is connected to a constant voltage source through a varistor. 2. The device according to claim 1, about t l and so that, with the aim Q extends the linear range of sensitivity adjustment of a photovoltaic device when working with elevated levels of background radiation, controlled semiconductor elements are made on thyristors. Sources of information taken into account in the examination 1. US patent W 3898452, cl. 250-207, published. 1974. 0 2. USSR inventor's certificate No. 481084, cl. H 01 J 39/14, 1975 (prototype).