SU1589073A1 - Photoelectric transducer - Google Patents

Abstract

The invention relates to a technique for measuring the intensity of electromagnetic radiation and can be used as part of devices for studying the spectral and spatial-temporal characteristics of sources of electromagnetic radiation. The purpose of the invention is to increase the speed and accuracy of measurements. The device contains a photodetector 1, a field-effect transistor 2, a load resistor 3, an operational amplifier 4 with a loop of 100% consecutive negative feedback, bias sources 5.6, feedback circuit 7, inverting amplifier 8. Due to the presence of feedback circuit 7, connected to one of the outputs of the photodetector 1, and the connection of the output of the operational amplifier 4 with the other output of the photodetector, the potential difference at the last during the measurements remains constant. As a result, the distortions arising from the recharge of the photoreceiver's own capacity are eliminated, and the speed of the device is increased. 1 il.

Description

The invention relates to techniques for measuring the intensity of electromagnetic radiation and can be used as part of devices for the emission of spectral and spatio-temporal characteristics of sources of electromagnetic radiation.

The aim of the invention is to increase the speed and accuracy of measurements.

The drawing shows a block diagram i of the proposed photovoltaic; converter.

The photoconverter contains a photodetector 1, a field effect transistor 2, a load resistor 3, an operational amplifier 4 with a loop of 100% serial negative feedback: voltage sources 5 and 6 cm; ’- 20; connections, feedback circuit 7, inverting amplifier 8.

The device operates as follows.

Under the action of the electromagnetic radiation flux ¹ incident on the photo- 25 receiver 1, a current flows in the gate circuit of the field-effect transistor 2, the magnitude of which is proportional to the intensity of the radiation flux. Using the negative feedback circuit 7, the input signal is converted into a form convenient for further processing, for example, the conversion of current - voltage or charge - voltage, depending on the type of photodetector '1. 35

The voltage in the gate circuit of the field-effect transistor 2 is repeated at its source and goes to the input of the operational amplifier 4, the output channel of which is supplied to the second output of the photodetector 1, the drain of the field-effect transistor 2 and the load resistor 3 through the sources 5 and 6 of the bias voltage 40. The gain K1 of the operational amplifier 4, covered by a loop of 100% 45 sequential negative feedback, is expressed by the formula:

K1 = K2 / 1 + K2, (1) where K2 is the gain of the operational amplifier 4 without a feedback loop.

The value of K2 and modern instruments lies in the range 10 ⁴ - 10 ^ thus K1-1 up to the fifth - j sixth decimal place. The output signal of the operational amplifier 4 through a bias voltage source 6 is supplied to a load resistor 3, the terminal potentials of which coincide in amplitude and phase, due to which its equivalent resistance increases by a factor of K2 and amounts to 10 ⁷ - 10 ^e Ohm. The transfer coefficient of the source repeater KZ is

KZ = S1R1K2 / 1 + S1R1K2 where S1 is the slope of the current-voltage characteristic of the field-effect transistor;

R1 - load resistance, also increases compared to the prototype and with high accuracy (up to the sixth decimal place) is equal to one.

In addition, the output signal of the operational amplifier through the bias voltage source 5 is fed to the second output of the photodetector 1 and the drain of the field effect transistor 2. This closes the loop of the positive feedback feedback of the input stage of the photoelectric converter, the transmission coefficient of which is close to unity (internal resistance of the sources 5th 6 bias voltage can be selected arbitrarily small). The voltage of the signals at the terminals of the photodetector 1, the electrodes of the field effect Transistor 2 and the load resistor 3 coincide in amplitude and phase, and the potentials of these points differ by a constant value equal to the voltage of the sources of voltage 5 and 6 of the biasing voltage. No current flows in the circuit of the interelectrode capacitances of the photodetector 1, field-effect transistor 2, which results in a higher degree of compensation of these capacities compared to the prototype. The introduction of bias sources in the loop tracking positive feedback avoids the modulation of the useful signal caused by overcharging the capacitor in the circuit of the photodetector of the prototype.

The invention allows two to three orders of magnitude to increase the speed of the device and increase the accuracy of measurements.

Claims (1)

Claim A photoelectric converter comprising a photodetector, a field effect transistor, the gate of which is connected to one of the terminals of the photodetector, a load resistor included in the source circuit of the field effect transistor, an inverting amplifier and a negative feedback circuit made in the form of a passive element connected between the gate of the field effect transistor and output of an inverting amplifier, characterized in that, in order to increase the speed and accuracy of measurements, an operational amplifier is introduced into it, covered by a loop of stop negative feedback, the non-inverting input of which is connected to the source of the field-effect transistor, and the output is connected to the input of the inverting amplifier, and two sources of bias voltages, two opposite-polarity outputs of which are connected to the output of the operational amplifier, and the other two to the drain and load resistor of the field-effect transistor and the second output of the photodetector through one of the bias sources is connected to the output of the operational amplifier. Compiled by A. Gruzinov