SU1401559A1 - Broad-band current amplifier - Google Patents

Abstract

This invention relates to a radio measuring technique. The purpose of the invention is noBbiujeHHe accuracy of compensation of the frequency response in a wide temperature range. To achieve the goal, a constant voltage source 15, a temperature sensor 16, a subtraction unit 17, a voltage divider 18, a bias voltage driver 19 are entered into the device. The former 19 is configured on an operational amplifier 20, a resistor x 21 and 22, an additional control current generator 23. As a result of the temperature stabilization of the gain and bandwidth, the shape of the frequency response of the wideband current amplifier remains unchanged over a wide temperature range. In the case of using a temperature sensor 16 with a digital output of a source 15 function (memory element), a subtractor 17 and a voltage divider 18, b. made by microprocessor controller. I h. the item of f-ly, I ill.

Description

YOU)

about -

This invention relates to radio metering technology and can be used in wideband amplifiers for oscilloscopes and digital voltmeters.

The purpose of the invention is to improve the accuracy of compensation of the amplitude-frequency characteristic JIKI in a wide range of temperatures.

The drawing shows a structural electrical circuit of a broadband current amplifier.

The voltage at the output of the constant voltage source 15 is set such that, at a normal temperature (K), the voltage at the output of the subtracting unit 17 is zero. At the same time, the Broadband Current Amplifier, the IQ-Finder 15, performs the functions of the input stage cascade 1, performed on the first 2 and second 3 output transistors, transistors 4 and 5 in the diode switching on, the first 6 and second 7 controlled current generators, N stages 8i , ..., 8 amps,

each of which is made on the first, 5th temperature, second, third, fourth transistors 9-12, respectively, U of the third controlled current generators 13, the first, second, third controlled generators 6, 7 and 13 of the current respectively ., are exactly equal to the resistors and the resistor 14 in their emitter circuit, a constant voltage source 15, a temperature sensor 16, a subtraction unit 17, a voltage divider 18, a bias voltage driver 19, performed on the operational amplifier 20, the first 21, and the second 25 rum 22 resistors, optional yuschem gen1eratore control current 23, performed on the transistor and resistor in its emitter circuit.

Broadband current amplifier operates as follows.

The amplified signal is fed to the input of the input stage 1. The voltage increment on the p - “- junctions of the first pair of differentially connected transistors 4 and 5 leads to a relative change in current

since it saves the set value of the voltage regardless of changes in the external conditions, i.e. it remembers the voltage corresponding to the output signal of the temperature sensor 16 at the current amplification factor / (, (at low frequencies) and the bandwidth of the A / wideband amplifier current corresponds to C, (/, + / 2 + ... + / N) // i; & C. (/ 2 -) / Ko,

where / 1, / 2, ..., / „are the total emitter currents of the second differential pair of transistors 2, 3 and 12, 11;

- gain coefficient of one cascade of gain;

- number of stages of amplification.

To

1-1

4-1

N

thirty

and its bandwidth D1, depending on the cut-off frequency of the transistors. With a change in ambient temperature

The quantities Ki and L / determine the shape of the amplitude-frequency characteristic of the broadband current amplifier. Therefore, to stabilize the shape of the amplitude-frequency characteristic over a wide range of temperatures, it is stabilized.

through these peVexVdy. A series of 35 gain factors K /, which depends on the p - «- transitions (base-emitter) transis, depends on the ratio of the quiescent currents of all cascades of tori 4 and 5 of the first differential pair the input cascade 1 pair is kept in balance, then when the input 40 is applied, the cut-off frequency / transistor of the signal changes to the p-junction with a small initial value inversely proportional to the relative

a change in temperature T (Kelvin) L /., ЗЗГ / Г. On the other hand, the cut-off frequency / is determined by the current 7 y flowing through the transistors, and

we create rn-junctions of transistors 9 45 the value of the boundary frequency f directly pro-and 10 and transistors 11 and 12 of the cascades 8i, ... proportionally to the flowing current /, i.e.

where t is the proportionality coefficient (Hz / A). This makes it possible to compensate for temperature changes in the cut-off frequency / transistors corresponding to the 20 in the driver 19 stabilizes 50 by changing the current through it, and the collector current of the generator 23, the connected change must be direct to the output of the operational amplifier 20, regardless of the temperature variation of the voltage emitter base and supply voltage. In this case, the voltage on -g., G

The bases of the transistors of the generators 6, 7 and 13 55 p are set by the transfer coefficient to the voltage equal to the base of the transistor genus 17 subtraction, the rator 23 in the driver 19. Consequently, the voltage drop across all resistors (transistors 4 and 5) is formed by an increased increment current to p - "- the transitions of the second differential pair of transistors 2 and 3. Similar balanced circuits gain.

At normal ambient temperature (K), the operational amplification is relative to the relative change in temperature AG / 7. The coefficient of proportionality between the relative changes in temperature and current through a transistor. When the ambient temperature is different from normal, then the output

pax 14 is equal and this equality is preserved regardless of the magnitude of the temperature variation of the emitter-base voltage of the transistors of the 6, 7 and 13 generators and the supply voltage.

The voltage at the output of the constant voltage source 15 is set such that, at a normal temperature (K), the voltage at the output of the subtracting unit 17 is zero. In this case, the source 15 performs the functions of an element that is equal to the temperature

since it saves the set value of the voltage regardless of changes in the external conditions, i.e. it remembers the voltage corresponding to the output signal of the temperature sensor 16 at normal temperature, equal to

The gain of the current / (, (at low frequencies) and the passband A / of the broadband current amplifier, respectively, are equal to

C, (/, + / 2 + ... + / N) // i; & .С (/ 2 -) / Ko,

where / 1, / 2, ..., / „are the total emitter currents of the second differential pair of transistors 2, 3 and 12, 11;

- gain coefficient of one cascade of gain;

- number of stages of amplification.

To

1-1

4-1

N

and its bandwidth D1, depending on the cut-off frequency of the transistors. With a change in ambient temperature

 the gain factor K /, which depends on the ratio of the quiescent currents of all the stages, the cut-off frequency / of the transistors varies inversely with respect to

current change through it, and the change should be directly -r -., g

 p is defined by the transfer coefficient of subtraction block 17,

proportional to the relative change in temperature AG / 7. The coefficient of proportionality between the relative changes in temperature and current through the transistor p is determined by the transfer coefficient of the block 17

When the ambient temperature is different from normal, then the output

the divider 18 is formed by a voltage proportional to the relative change in temperature AG / G (Kelvin). The input proportional to the output of block 17 receives a voltage proportional to the absolute change in temperature AG, and the input to the divider is supplied to a voltage proportional to the absolute value of the temperature T of the environment. At the same time, the current of the transistor of the generator 23 in the driver 19, and with it the currents of all the transistors of the generators 6, 7 and 13, determining the quiescent currents of the respective stages, changes in proportion to the relative temperature change in Kelvin. Therefore, the temperature variations of the cut-off frequency / transistors are compensated for by the simultaneous change in the quiescent current A / N of all the transistors. As a result of the stabilization of the magnitude /, the bandwidth A / of the broadband current amplifier is constant over a wide range of temperatures. At the same time, to maintain the overall gain in the broadband current amplifier, the same relative change in the collector currents (quiescent currents) of the transistors of all stages is provided.

As a result of the temperature stabilization of the gain and bandwidth, the shape of the amplitude-frequency characteristic of the broadband current amplifier remains unchanged over a wide range of temperatures.

In the case of using a temperature sensor with a digital output of the function of source 15 (memory element), subtractor 17, and voltage divider 18 can be performed by a microprocessor controller.

Claims (2)

1. A broadband current amplifier containing an input stage and N amplification stages, each of which is made on the first and second transistors connected according to a common base circuit, the first and second transistors of all the stages connected in series with a constant current of the same name, respectively, and the second output transistors of the input cascade connected according to the common emitter circuit, the emitters of which are combined and connected to the first power supply bus through the first controlled current generator, the bases connected via the corresponding transistors in the diode connection, the emitter connection point of which is connected through the second controlled current generator to the first power supply bus, 0, in each stage of amplification, the emitters of the first and second transistors are connected to the bases of the third and fourth transistors, respectively, the emitters of which are combined and through the third controlled current generator are connected to the first power supply terminal, and the collectors are connected to the collectors of the second and first transistors, respectively, different In order to increase the accuracy of the amplitude-frequency response compensation over a wide temperature range, a constant voltage source has been introduced The unit, the subtraction unit, the voltage divider and the bias voltage driver, the output of which is connected to the control inputs of the first, second and third controlled current generators, while the outputs of the constant voltage source and the temperature sensor are connected to the corresponding inputs of the subtractor, output which is connected to the input of the dividend A voltage divider, the input of which divider is connected to the output of the temperature sensor, and the output to the control input of the bias voltage driver. 2. Amplifier according to claim 1, characterized in that the bias voltage driver 5 is made on an operational amplifier and an additional controllable current generator, the output of which is connected to the non-inverting input of the operational amplifier and through the first resistor to the reference voltage source bus, the inverting input 0 which is connected to the common bus and also to the second resistor, the first terminal of which is connected to the non-inverting input of the operational amplifier, and the second output is the control input of the bias voltage driver. five