SU1336195A1 - Amplifier - Google Patents

Abstract

The invention can be used to amplify alternating voltage and provides an increase in input resistance and gain. The amplifier contains n series-connected cascades 1 with direct connections, resistors 2, 5, capacitor 3, transistors (T) 4, 7, 10, current setting resistor 8 and resistive divider 11. The input variable signal is amplified by all stages 1. With the output of the amplifier to the input of the first stage through the resistors 2, 5 gives a signal of the total negative. direct current feedback. The current source, made on T 4, 7 and the current-carrying resistor 8, maintains at the output of the amplifier a voltage equal to half the voltage of the power source. The alternating voltage from the output of the amplifier through the resistor 2 and the capacitor 3 is applied to the base T 4 and causes antiphase changes in its collector current. Since the total current flows through T 4, 10, the transfer of the ac signal from the output to the input of the amplifier is excluded. This leads to an increase in the input impedance and gain coefficient of the usher in the medium frequency range. 1 il. l Output with co Oi SO ate

Description

one

The invention relates to an amplifier technique and may be used as a wideband AC voltage amplifier.

The purpose of the invention is to increase the input resistance and the gain.

The drawing shows a circuit diagram of an amplifier.

The amplifier contains n series-connected cascades 1 with direct connections, the pth cascade being made on a transistor according to a common collector circuit, the first resistor 2, the capacitor 3, the first transistor 4, the second resistor 5, the first bus 6 of the power supply, the second transistor 7, current supply resistor 8, second power supply bus 9, third transistor 10, resistive divider 11.

The amplifier works as follows.

The AC input signal is fed to the input of the first cascade and amplified by all n series-connected cascades 1. From the amplifier output to the input of the laser cascade, through the first 2 and second 5 resistors, a common negative feedback (OOS) signal is applied, providing the high stability of the electrical control of the series-connected cascades 1. The current source, made on the first 4 and second 7 transistors and the current-carrying resistor 8, maintains a constant voltage at the output of the amplifier olovine voltage source pi Tani, regardless of the ambient temperature and the stress on the first 6 and the second power source 9 and tire.

The alternating voltage from the output of the amplifier through the first resistor 2 and the capacitor 3 is applied to the base of the first transistor 4 and causes antiphase changes in its collector current. In the mid-frequency region, the input impedance of the cascade on the first transistor 4 is approximately equal to the differential resistance of its emitter junction, since the cascade is covered by a 100% parallel OOC in alternating voltage. The signal at the base of the first transistor 4 is determined by the output voltage of the amplifier, weakened by a voltage divider from

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The first resistor 2 and the input resistance of the first transistor 4. The differential resistance of the third transistor 10 in the diode connection is also determined by the resistance of its emitter junction, and since the total current flows through the first 4 and third 10 transistors, this resistance is almost equal to the input resistance of the cascade on the first transistor 4, and the voltage drop on the third transistor 10 is equal to the voltage drop on the emitter junction of the first transistor 4. As a result, the alternating voltage on the collector is the first- transistor 4 is practically zero, and the transmission of the AC signal output from the input amplifier is eliminated. This leads to an increase in its input impedance and gain in the medium frequency range. The resistive divider 11 provides isolation of the input of the first transistor 4 from the shunt effect of the second transistor 7, increases the effective capacitance value of the capacitor 3 and ensures that the first 4 and second 7 transistors operate in the same DC mode.

Claims (1)

Invention Formula An amplifier containing p series-connected cascades with direct connections, the p-th stage of the transistor according to a common collector circuit, the input of the first stage is the amplifier input, and the n-th output is the amplifier output and is connected to the first output the first resistor, the second terminal of which is connected via a capacitor to the base of the first transistor, the collector of the first transistor is connected via the second resistor CJDinen to the input of the first stage, and the emitter is connected to the first power supply bus and to the emitter of the second port Anisistor, the collector of which is connected to the second power supply bus through a current-supplying resistor, characterized in that, in order to increase the input resistance and gain, a third transistor and a resistive divider are inserted, while the resistor-divider leads are connected between the bases of the first and second transistors, and the tap is connected to 1336195 the collector of the second transistor, the base of the first resistor, and the emitter of the co- and collector of the third transistor are combined with the collector of the first transistor and are connected to the second of the transistor.