SU374718A1 - RELAXATION RADIATION DETECTOR - Google Patents

Description

one

The invention relates to computing and automation.

Relaxation radiation detectors are known, which contain a transistor with resistive bias circuits, limiting and feedback, a luminescent diode included in the collector circuit of the transistor, and two photodiodes, the first of which is connected to the collector-base circuit transistor, and power supply.

The proposed device differs from the known ones in that a nonlinear capacitance (e.g., a zener diode) is inserted in it, connected between the emitter of the transistor and the positive pole of the power source.

This allowed us to increase the sensitivity and reduce the relaxation time.

The drawing shows a diagram of the proposed device.

The device contains a transistor 1 with resistive bias circuit 2, limiting 3 and feedback 4, a luminescent diode 5 included in the collector circuit of transistor 1 and two photodiodes 6 and 7, connected inversely to the feedback circuit: the first is in the circuit the collector base, and the second into the base-emitter circuit, and the power source 8.

In addition, the device contains a non-linear capacitance 9 (for example, a reverse polarity zener diode), which is connected between

Emster transistor 1 and the positive pole of the power source 8.

The device works as follows.

In the autogeneration mode, the operating point of the transistor 1 is selected on the negative resistance between i-f LJf, where U-f is the avalanche voltage of transistor 1, and is the voltage corresponding to the open state of the transistor /.

When the operating point is close to AND and the minimum collector current / k flows in transistor 1, the voltage on the collector of transistor 1 is approximately equal to the voltage of power supply 6. At the same time, the absolute value of absolute voltage is applied to photodiode 6, which corresponds to the minimum non-linear value capacity.

At the emitter of the transistor 1, the voltage is zero, and the capacitance of the Zener diode 9 and the photodiode 7 is non-linear and has a maximum value. 1 luminescent diode 5 does not emit light signals at the output, and in photodiodes 6

and 7 tempo flows.

When the operating point is near the point, the maximum collector current flows in the transistor /, the luminescent diode 5 produces a light signal at the output, and the device output accordingly positive and negative electrical signals, as the minimum voltage is set at the collector of transistor 1.

The limiting resistor 3 is selected to be less than the bias resistor 2. If at the output of the device there is no need to receive positive electrical signals, then the resistor 5, in the value limit, is chosen to be zero.

The maximum amplitude of negative signals at the output is obtained at the maximum increment of nonlinear capacitance 9.

At the end of charge of nonlinear capacitance 9, the charge current decreases almost to zero, so the collector current will be equal to the photodiode current 6. At the same time, the operating point will move again to the side, i / p and when the condition is met / k, / boom, where / ud. - the holding current to keep the transistor 1 in the open state, the transistor 1 is closed and the original position is restored.

After closing the transistor, the non-linear capacitance 9 will be discharged through the bias resistor 2, and the operating point moves to t / p, the transistor / opens, and so on, so the output receives undamped relaxation oscillations. The duration of each pulse can be obtained from several nanoseconds to several tens of microseconds, depending on the size of the capacitance included in the emitter circuit.

For the proposed device in standby mode, the condition Uf and Cg I- is observed. When the photodiode 6 is illuminated, a photocurrent flows in ngm, and the potential on the base rises above the cut-off point of the transistor /, / 7, h and when The / Ki I, the device switches and at its outputs signals appear, the duration of which is proportional to the resistance of the bias resistor 2 and the nonlinear capacitance 9, and at the output P1 a light pulse proportional to the current is. In this mode, the code

The number of pulses is determined by the formula

P

where n is an integer.

The inclusion of the Zener diode 9 as a nonlinear capacitance increases the sensitivity of the device to the output signals, since for

The input signals are non-linear, the capacitance of the Zener diode 9 by the time of opening of the transistor 1 bypasses the resistor 2, i.e. the negative feedback through the emitter of the transistor / will be zero. Therefore, if the operating point is near f / z. To open transistor 1, an electric signal of small power must be applied to its input.

Subject invention

A relaxation radiation detector containing a transistor with resistive bias, limiting and feedback circuits, a luminescent diode included in the collector circuit of the transistor, and two photodiodes, the first of which is connected to the collector-base circuit and the second is connected to the base-emitter circuit of the transistor and a power source different in that

that, in order to increase the sensitivity and decrease the relaxation time, a nonlinear capacitance (for example, a zener diode) is inserted into it, connected between the emitter of the transistor and the positive pole of the source

nutrition

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