SU1406727A1 - Amplifier of solid-body photodetector signals - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to increase the signal to noise ratio. The amplifier contains transistors 1-4, resistors 5-8, capacitors 9, 10 and 11, inductor 12 and current sensors 13 and 14. The feedback signal from the sensor 13 through the resistor 6 to the emitter circuit of the transistor 4 causes a decrease in the equivalent input resistance of the amplifier. This provides good amplitude-frequency properties and contributes to a deeper suppression of clock interference by a parallel circuit formed by a choke 12 and a capacitor 9. Setting the mode of the photoreceiver output circuit with the help of a transistor 4 connected according to a common base circuit ensures its high output impedance. current with a relatively large absolute current value. This necessitates the use of a high-voltage power source and provides an increase in the signal-to-noise ratio. 1 il. (L Ci to -

Description

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The invention relates to radio engineering and can be used to amplify television signals taken from solid-state photodetectors based on charge-coupled devices.

The purpose of the invention is to increase the signal to noise ratio.

The drawing shows a circuit diagram of the proposed signal amplifier of a solid-state photodetector.

The amplifier of the signals of a solid-state photodetector contains the first, second, third and fourth transistors 1-4, the first, second, third and fourth resistors 5-8, the first, second and third capacitors 9, 10 and II, choke 12, the first and second sensors 13, 14 current.

Amplifier signal solid-state photodetector works as follows.

An electrical signal from a solid-state photodetector based on devices with charge coupling through a parallel circuit formed by the choke 12 and the first capacitor 9 is fed to the base of the first transistor 1.

An amplifier operating with a high output impedance of the signal source (the output transistor of a solid-state photodetector) must accept the current, not the voltage, since with a small input impedance, the current given by the output transistor of the solid-state photodetector is the greatest, and the effect on the amplitude the frequency response of the parasitic capacitances brought to the amplifier input is the smallest. The low input impedance of the proposed signal amplifier of a solid-state photodetector is provided by a feedback loop, including an input emitter voltage follower on the first transistor 1, the base-collector junction of the second transistor 2 and the fourth transistor 4. Although the output impedance of the fourth transistor 4 is connected according to with a common base, large, the flow of the feedback signal from the first current sensor 13 through the second resistor 6 to the emitter circuit of the fourth transistor 4 causes a decrease in The equivalent input resistance of the amplifier signals the solid-state photodetector to a value on the order of 100 to 300 ohms. This provides good amplitude-frequency properties and contributes to a deeper suppression of clock interference by a parallel circuit formed by the choke 12 and the first capacitor 9. Establishing the output circuit mode of the solid-state photodetector using the fourth transistor 4, which ensures its high output DC resistance with a relatively large absolute current value. 1st most exclude06727

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It requires the use of a high-voltage power source, similar to that in the prototype, and provides a good signal-to-noise ratio.

To eliminate the need to select the operating point of the signal amplifier of a solid-state photodetector, the mode along the base circuit of the fourth transistor 4 is dependent on the potential of the emitter circuit of the first transistor 1, which is determined, in turn, by the output resistance of the transistor solid-state photodetector, its cut-off potential, and parameters a fault transistor in the photodetector. If the output impedance of the photodetector is small, the potential of the emitter circuit of the first transistor 1 decreases, which causes an increase in the current of the fourth transistor 4. If the output impedance of the photodetector is large, then the current of the fourth transistor 4 decreases. The

It is most possible to significantly reduce the effect of the parameter variation and eliminate the mode adjustment for different samples of solid-state photodetectors.

The circuit for automatic adjustment of the mode is valid only at a constant component; the variable component of the signal is filtered by the circuit from the second capacitor 10 and the first resistor 5. The signal is amplified by the voltage of the third transistor 3, connected in accordance with a common base circuit. For

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matching the high output impedance of the photodetector and the low input impedance of the third transistor 3, an input voltage follower is used on the first transistor 1 and a second, a voltage across the second transistor 2. The amplifier of the signals of the solid-state photodetector is well protected from interference from the power supply bus. Interference penetration into the input circuit is prevented by the high resistance of four fourth transistor 4. The output push-pull emitter follower on the second and third transistors 2, 3 is also insensitive to interference due to the low output impedance of the first transistor 1. Thus, the proposed amplifier of the solid-state photodetector improves the primary output parameter — signal-to-noise ratio — without using a high-voltage power source; moreover, it will reduce the The accuracy of the pickups on the power supply, as well as through the automatic setting of the mode of operation of setting the mode of direct current.

Claims (1)

55 Formula of Invention Amplifier of signals of a solid-state photodetector containing successively 45 the connected input voltage follower on the first transistor and the output stage, on the second and third transistors connected in series with DC, having a different structure and emitters of which are combined, as well as the first, second, third and fourth resistors, first, second and third capacitors characterized in that, in order to increase the signal-to-noise ratio, a choke and a fourth transistor of the same structure as the first and third transistors are inserted into it, the output stage is made with the first and second current sensors in collector circuits x, respectively, of the second and third transistors, while the choke is connected in parallel to the first capacitor and the base of the first transistor, the emitter of which is Dinen with the base of the second transistor and through the first resistor - with the base of the fourth transistor, the collector of which is connected to the base of the first transistor, and the emitter through the second resistor - to the collector of the second transistor, a third resistor is connected between the base and the collector of the third transistor, and : retigo transistors - the fourth resistor, the second capacitor is connected between the base of the fourth transistor and the power supply bus, the third capacitor is connected between the base of the third transistor and the common source, the second connection point Neny choke and a first capacitor is input, and the collector of the third transistor - Bb stroke amplifier signals photodetector solid.