RU2390919C1 - Controlled ac amplifier - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention may be used as broadband amplifier, coefficient of transmission by voltage of which depends on the level of control signal (u_y). Such devices are used in structure of analogue microchips of various functional purpose, systems of automatic amplification control, analogue signal multipliers, etc. Controlled AC amplifier (CACA) comprises the first (1) input transistor (T), base of which is connected to the main (2) input of CACA, the second (3) input T, base of which is connected to control inlet (4) of CACA, dipole (5) of local negative feedback (NFB) connected between emitters of the first (1) and second (3) T, load circuit (6) connected to collector of the first (1) and second (3) T and outlet (7) of CACA, the first (8) blocking capacitor connected by alternating current between emitter of the first (1) T and common bus (9) of supply sources (SS), the first (10) current stabiliser connected to emitter of the first (1) T, the second (11) current stabiliser connected to emitter of the second (3) T, the second blocking capacitor (12). The circuit comprises the first (13) and second (14) additional T, emitters of which are connected to each other via additional dipole (15) of NFB and are connected to according first (16) and second (17) current stabilisers, base of the first (13) additional T is connected to control input (4) of CACA, the base of the second 14 additional transistor is connected to common bus (9) of SS, besides the first (10) current stabiliser is arranged in the form of controlled current stabiliser, having non-inverting input (18), and the second (12) blocking capacitor is connected between emitter of the second (14) additional T and non-inverting input (18) of the first (10) current stabiliszer.

EFFECT: improved ratio of control signal suppression in wide range of frequencies.

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Description

The present invention relates to the field of radio engineering and communications and can be used as an AC amplifier, the voltage transfer coefficient of which K _u depends on the level of the control signal (u _y ). Such devices are used in the structure of analog microcircuits for various functional purposes, automatic gain control systems, analog signal multipliers, etc.

In modern adaptive SF blocks of communication systems, a classical differential cascade with a local negative feedback resistor is widely used as a controlled amplifier. Moreover, on its basis, various modifications of controlled amplifiers are performed [1-26].

The closest in technical essence to the claimed device includes a controlled differential cascade described in US patent No. 5.126.586, figure 1. It contains the first 1 input transistor, the base of which is connected to the main 2 input of the controlled amplifier, the second 3 input transistor, the base of which is connected to the control input 4 of the controlled amplifier, two-terminal 5 local negative feedback connected between the emitters of the first 1 and second 3 input transistors, load circuit 6, connected to the collector of the first 1 and second 3 input transistors and the output 7 of the controlled amplifier, the first 8 blocking capacitor connected by alternating current between the emitter of the first 1 input one transistor and a common bus 9 power supplies, the first 10 current stabilizer connected to the emitter of the first 1 input transistor, the second 11 current stabilizer connected to the emitter of the second 3 input transistor, the second blocking capacitor 12.

A significant drawback of the known controlled amplifier (SU) is that it does not provide effective suppression of the control signal at either low or high frequencies. This does not allow performing on its basis various functional units of modern communication systems, which are characterized by one of the most important requirements - the absence of harmonic components of the control signal u _at the output.

The main objective of the invention is to increase by several orders of magnitude the suppression ratio of the control signal in a wide frequency range.

This goal is achieved by the fact that in the controlled AC amplifier (Fig. 1), containing the first 1 input transistor, the base of which is connected to the main 2 input of the controlled amplifier, the second 3 input transistor, the base of which is connected to the control input 4 of the controlled amplifier, two-terminal 5 local negative feedback connected between the emitters of the first 1 and second 3 input transistors, a load circuit 6 connected to the collector of the first 1 and second 3 input transistors and the output 7 of the controlled amplifier, the first 8 blocking capacitor connected by alternating current between the emitter of the first 1 input transistor and the common bus 9 power sources, the first 10 current stabilizer connected to the emitter of the first 1 input transistor, the second 11 current stabilizer connected to the emitter of the second 3 input transistor, the second blocking capacitor 12, new elements and connections are provided - the first 13 and second 14 additional transistors are introduced into the circuit, the emitters of which are connected to each other through an additional negative terminal two-terminal 15 communication and connected to the corresponding first 16 and second 17 additional current stabilizers, the base of the first 13 additional transistor is connected to the control input 4 of the controlled amplifier, the base of the second 14 additional transistor is connected to a common bus 9 of power sources, and the first 10 current stabilizer is made in the form of a controlled stabilizer a current having a non-inverting input 18, and the second 12 blocking capacitor is connected between the emitter of the second 14 additional transistor and the non-inverting input 18 of the first 10 stable current isator.

In Fig.1 shows a diagram of the UU-prototype, and Fig.2 is a diagram of the claimed UU in accordance with the claims.

In Fig.3 shows a diagram of the control unit of Fig.2 in a computer simulation environment PSpice on models of integrated transistors of the Federal State Unitary Enterprise NPP Pulsar. The results of its modeling are shown in figure 4 - 7:

- the dependence of the gain on the voltage K _u from the control voltage U _y (figure 4) in the range of medium frequencies;

- the dependence of the gain on the voltage K _u from the frequency at different values of the control voltage U _y (figure 5);

- the dependence of the output sinusoidal voltage UU from time to time for different values of the alternating control voltage u _y = U _y sinω _y t;

- the dependence of the control voltage suppression coefficient (K _{n O} = u / u _y) on frequency.

The controlled AC amplifier (Fig. 2) contains the first 1 input transistor, the base of which is connected to the main 2 input of the controlled amplifier, the second 3 input transistor, the base of which is connected to the control input 4 of the controlled amplifier, two-terminal 5 local negative feedback connected between the emitters the first 1 and second 3 input transistors, a load circuit 6 connected to the collector of the first 1 and second 3 input transistors and the output 7 of the controlled amplifier, the first 8 blocking capacitor, connected across the current between the emitter of the first 1 input transistor and the common bus 9 of power supplies, the first 10 current regulator connected to the emitter of the first 1 input transistor, the second 11 current stabilizer connected to the emitter of the second 3 input transistor, the second blocking capacitor 12. The first 13 and second 14 additional transistors, the emitters of which are connected to each other through an additional two-terminal 15 negative feedback and connected to the corresponding first 16 and second 17 additional stable current congestion, the base of the first 13 additional transistor is connected to the control input 4 of the controlled amplifier, the base of the second 14 additional transistor is connected to a common bus 9 of power sources, and the first 10 current stabilizer is made in the form of a controlled current stabilizer having a non-inverting input 18, and the second 12 blocking a capacitor is connected between the emitter of the second 14 additional transistor and the non-inverting input 18 of the first 10 current stabilizer. In a particular case, the current stabilizer 10 is made on a transistor 19 and a resistor 20.

Consider the operation of a controlled amplifier (figure 2).

In the medium frequency range, the signal amplification u _x along the main input 2 for u _y = 0 is provided by the transistor 1, turned on according to the traditional

common emitter circuit:

where R _n.eq - equivalent resistance of the load circuit 6;

φ _t ≈25 mV - temperature potential;

I ₁₀ - static current of the emitter of transistor 1;

r _e1 = φ _t / I ₁₀ - resistance of the emitter junction of the transistor 1.

If the voltage U _y at the control input 4 and changes by the value u _y , then the current through the two-terminal 5 also changes:

where R ₅ is the resistance of the two-terminal 5.

At very low frequencies (f _y << f _x) increment current i _y completely enters the emitter of transistor 1, and further - a load circuit 6. As a consequence, when u slow changes _in load 6 provided complete compensation almost equal currents i _3.y and i _к.y , “generated” by control signals u _у :

Therefore, in the circuit 2 at slow changes u _have provided a high level of suppression control signal u _y, which is a prerequisite for constructing high on its base controlled amplifiers, modulators, analog multipliers, etc. However, with increasing frequency ω _of the control signal (u _y = U _y sinω _y t), not all increment i _{y is} completely transmitted to the emitter of transistor 1 - part of this current i _8.y “branches” into the blocking capacitor 8. As a result, the second term in equation (3) decreases, which worsens the suppression of the control signal u _y in the output circuit.

, близкий по величине току i_8.y, причемIn the inventive device due to the new elements and the connections between them, the current is added to the emitter circuit of the transistor 1

close in magnitude to the current i _8.y , and

where K _i10 ≈1 is the current transfer coefficient of the current stabilizer 10 at input 18.

, то на основании первого закона Кирхгофа для эмиттерной цепи транзистора 1 можно получить, что комплекс тока эмиттераIf we take into account that with the same resistance of the two-terminal devices 5 and 15, the same capacitors 8 and 12, as well as in the unit gain K _i10 = 1, the equality

, then on the basis of the first Kirchhoff law for the emitter circuit of transistor 1, we can obtain that the emitter current complex

Therefore, the current in the load resistor 6, due to the voltage u _y , is close to zero

i _6.y = i _K.u -i _3.y ≈0.

Thus, in the circuit of FIG. 2, the frequency dependence of the suppression coefficient of the control signal K _p , which remains sufficiently small in a wider frequency range than in the circuit of FIG. 1, is compensated.

This theoretical conclusion is confirmed by the results of computer simulation of the circuit of Fig.2, shown in Fig.7.

BIBLIOGRAPHIC LIST

1. US patent application No. 2004/0183599.

2. US Patent Application No. 2004/0178850.

3. US Patent Application No. 2006/0044064.

4. US Patent Application No. 2008/0088374.

5. US Patent No. 4,575.687.

6. US patent application No. 2005/0179493.

7. US patent No. 6.456.142.

8. US Patent No. 5.184.088.

9. US Patent No. 6,703.899.

10. US patent application No. 2008/0191803.

11. US patent No. 6.525.606, Fig.6.

12. US patent No. 6.980.054, figure 4.

13. US patent No. 6.980.053.

14. US patent application No. 2005/0258900.

15. US patent application No. 2003/0011429.

16. US patent No. 6.972.625.

17. US patent application No. 2006/0022748.

18. US patent No. 5.157.360.

19. US patent application No. 2005/0038615.

20. GB patent 2,318,470.

21. US patent No. 5.126.586.

22. U.S. Patent 4,511,852.

23. U.S. Patent 4.881.043.

24. US patent No. 6.891.436, figure 1.

25. US patent No. 6.933.783, Fig.20, 21.

26. US patent No. 4.267.518.

Claims (1)

A controlled AC amplifier containing the first (1) input transistor, the base of which is connected to the main (2) input of the controlled amplifier, the second (3) input transistor, the base of which is connected to the control input (4) of the controlled amplifier, two-terminal (5) local negative feedback included between the emitters of the first (1) and second (3) input transistors, a load circuit (6) connected to the collector of the first (1) and second (3) input transistors and the output (7) of the controlled amplifier, the first (8) blocking capacitor, including alternating current between the emitter of the first (1) input transistor and the common bus (9) of power supplies, the first (10) current stabilizer connected to the emitter of the first (1) input transistor, the second (11) current stabilizer connected to the emitter of the second ( 3) an input transistor, a second blocking capacitor (12), characterized in that the first (13) and second (14) additional transistors are introduced into the circuit, the emitters of which are connected to each other through an additional two-terminal (15) negative feedback and connected to the corresponding P to the first (16) and second (17) additional current stabilizers, the base of the first (13) additional transistor is connected to the control input (4) of the controlled amplifier, the base of the second (14) additional transistor is connected to a common bus (9) of power supplies, and the first ( 10) the current stabilizer is made in the form of a controlled current stabilizer having a non-inverting input (18), and a second (12) blocking capacitor is connected between the emitter of the second (14) additional transistor and the non-inverting input (18) of the first (10) current stabilizer.

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