RU2536378C2 - Broadband power amplifier with low level of nonlinear distortions and noise - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: broadband power amplifier with low level of nonlinear distortions and noise comprises an inverting output stage, the input of which is connected to the input of a device and an input voltage source, a load circuit connected to the output of the device, connected to the output of the inverting output stage. The input of the inverting output stage is connected to the input of the device and the input voltage source through a first additional resistor; between the input and the output of the device, there are series-connected second and third additional resistors, the common node of which is connected to the input of a non-inverting correction stage, the current output of which is connected to the input of the inverting output stage.

EFFECT: low level of nonlinear distortions and noise in the load circuit of a broadband power amplifier with an inverting output stage.

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Description

The invention relates to the field of radio engineering and communication and can be used as a device for amplifying analog signals in power, in the structures of buffer amplifiers and output stages for various functional purposes.

In modern electronic equipment, broadband inverting power amplifiers (SHUM) are used. They are the basis of various audio systems, radio transmitting devices, drivers, etc.

The closest in technical essence to the claimed technical solution is the classical scheme of the broadband power amplifier of figure 1, presented in patent US 5.237.526 fig.1b, 1a, the architecture of which is also present in a large number of other patents and monographs, for example [1-14] . In many practical cases, the output noise stage is implemented according to a circuit with parallel negative voltage feedback (Fig. 2), and this noise solution is classic for many of its applications [10-14].

A significant drawback of the known NOISE of FIG. 1 (FIG. 2) is that it has an increased level of non-linear distortion, which is characterized by a harmonic coefficient. This drawback is a consequence of the nonlinear operation modes of the transformers of the noise stage, as well as the influence on the nonlinear distortions of the sinusoidal signal of the final values of the maximum slew rate of the output noise voltage [11, 13, 14].

The main objective of the invention is to reduce the level of nonlinear distortion and noise in the load circuit of a broadband power amplifier with an inverting output stage.

The problem is solved in that in the broadband power amplifier of figure 1, containing an inverting output stage 1, the input of which is connected to the input of the device 2 and the input voltage source 3, the load circuit 4 connected to the output 5 of the device associated with the output of the inverting output stage 1 new elements and connections are provided - the input of the inverting output stage 1 is connected to the input 2 of the device and the input voltage source 3 through the first 6 additional resistor, between the input 2 and output 5 of the device are connected edovatelno connected to the second 7, and third 8 additional resistors, the common node 9 which is connected to the input of the correction stage 10, the current output 11 which is connected to the inverting input of the output stage 1.

The amplifier circuit of the prototype is shown in figure 1. Figure 2 presents an example of a practical implementation of the inverting output stage 1.

Figure 3 shows a diagram of the inventive device in accordance with claim 1, claim 2 and claim 3 of the claims.

Figure 4 shows a diagram of the inventive device of figure 3 for modeling the effect of correcting non-linear distortions due to the limited slew rate of the output voltage of the inverting output stage 1. In this case, the inverting output stage 1 is implemented here according to the traditional scheme on an operational amplifier with parallel voltage feedback on elements 12-17.

Fig. 5 shows a diagram of the broadband power amplifier of Fig. 3 in a PSpice environment with the resistance of the first 6 additional resistor R0 = R6 = 1 kOhm, as well as at the input signal frequency f _c = 1 kHz, u _in = 100 mV and noise voltage (u _OSH ) simulating nonlinear distortion: u _OSH = 10 mV, f _W = 5 kHz.

Figure 6 shows the dependence of the spectrum of the output voltage of the noise of Figure 5 on the frequency with the slope of the voltage-current converter 10 S = 0 (correction stage 10) and the resistance of the first 6 additional resistor R0 = R6 = 1 kOhm.

Figure 7 shows the dependence of the spectrum of the output voltage of the noise of Figure 5 on the frequency with the slope of the voltage-current converter 10 (correction stage 10) S = 1 cm and the resistance of the first 6 additional resistor RO = R6 = 1 kOhm.

On Fig presents the dependence of the spectrum of the output voltage of the noise in Fig. 4 from the frequency with the slope of the voltage-current Converter 10 (correction stage 10) S = 30 cm and the resistance of the first 6 additional resistor R0 = R6 = 1 kOhm.

9 is a diagram of the claimed device 2 in PSpice medium at the first resistor 6 additional resistor R0 = R6 = 50 ohm, u _Bx = 100mV, f _c = 1 kHz, u = 10 mV _err, f _w = 5 kHz .

Figure 10 shows the dependence of the spectrum of the output voltage of the noise of Figure 9 on the frequency when the voltage-current converter 10 (correction stage 10) S = 0 cm and the resistance of the first 6 additional resistor R0 = R6 = 50 Ohms.

Figure 11 shows the dependence of the spectrum of the output voltage of the noise of Figure 9 on the frequency when the voltage-current converter 10 (correction stage 10) S = 30 cm and the resistance of the first 6 additional resistor R0 = R6 = 50 Ohms.

A broadband power amplifier with a low level of nonlinear distortion and noise (Fig. 2) contains an inverting output stage 1, the input of which is connected to the input of the device 2 and the input voltage source 3, the load circuit 4 connected to the output 5 of the device associated with the output of the inverting output stage 1. The input of the inverting output stage 1 is connected to the input 2 of the device and the input voltage source 3 through the first 6 additional resistor, between the input 2 and output 5 of the device are connected in series to the second 7 and the third 8 additional resistors, the common node of which 9 is connected to the input of the correcting stage 10, the current output of which 11 is connected to the input of the inverting output stage 1.

In Fig. 3, in accordance with claim 2, as a correction stage 10, a voltage-current converter with high input and high output resistances can be used.

In figure 3, in accordance with claim 3 of the claims, a current amplifier with low input and high output resistances can be used as a correcting stage 10.

In Fig. 4, the inverting output stage 1 is implemented according to a circuit with parallel negative voltage feedback (resistors 12, 13) on the amplifying stages 14, 15 and frequency correction elements 16, 17 that determine the maximum slew rate of the output voltage of the output stage 1 (ϑ _out )

Consider the factors that determine the level of nonlinear distortion and noise in the inventive device of figure 3, in which the unwanted spectral components due to nonlinearities in the inverting output stage 1 are modeled by an equivalent source of nonlinear distortion u _osh .

The physical meaning of the noise suppression effect in the power amplifier of Fig. 3 is connected, firstly, with the allocation of an error signal u ₉ ~ u _os at node 9, which is proportional only to the level of undesirable spectral components u _os at the output of the non-inverting output stage 1 (in the case under consideration, frequency f _W = 5 kHz):

. $$u_9=\frac{R_7}{{\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="00000005.png"\; state="\{\{state\}\}">R</figure-callout>}}_7+R_8}{u}_{\mathrm{about}w}\approx \frac{u_{\mathrm{about}\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="00000005.png,00000007.png"\; state="\{\{state\}\}">w</figure-callout>}}}{2}$$

.

It should be noted that in node 9 there is no input amplified signal u _in with a frequency of 1 kHz considered in this case. This is due to the complete mutual subtraction in node 9 of its two antiphase components u _in and u _out = -u _in .

Dedicated thus error u ₉ ≈u _oui / 2 is introduced (due to resistor 6) in the input circuit of the output stage 1 and stage correction 10 with a high output impedance and compensates for voltage u _oui generated this output stage.

Let us further consider the simulation results. With a zero slope of the signal transmission in the correcting stage 10 (S ₁₀ = 0), the voltage of the noise and the spectral components of non-linear distortion _{ush is} completely transferred to the load 4. This is evidenced by the ratio of the amplitudes of the harmonics at output 5 (Fig.6): output voltage with a frequency of 5 kHz has an amplitude u _out = 10 mV.

With the introduction of a correction circuit 10 having a slope of S ₁₀ = 1 cm, the amplitude of the output harmonic of the device of FIG. 2 with a frequency of 5 kHz decreases 500 times from 10 mV to 20 μV (see FIG. 7). In most cases, this suppression u _err is sufficient for many applications. A further increase in the steepness S ₁₀ provides an even deeper attenuation of non-linear distortion and noise (Fig. 8). However, this is not always advisable.

With small values of the resistor resistance R0 = R6 = 50 Ohms (Fig. 9), noise suppression is also implemented in the basic circuit (Fig. 10, Fig. 11).

Thus, the claimed device has significant advantages in comparison with the prototype in the level of suppression of nonlinear distortion and noise. In addition, as the simulation shows, the proposed noise control structure makes it possible to increase the maximum slew rate of the output voltage of the device as a whole with small values of ϑ _output in the output inverting stage 1.

Information sources

1. Patent RU 2274946 fig.1b.

2. Patent US 5.512.856.

3. Patent US 5.237.526.

4. Patent US 6.707.339.

5. Patent application US 2006/0087369 fig.6.

6. Patent application US 2005/0231277 fig. 1.

7. Patent US 4.215.317.

8. Patent application US 2005/0024141.

9. Patent US 6.127.888.

10. Patent US 5.745.587.

11. Polonnikov D.E. Operational amplifiers: Principles of construction, theory, circuitry [Text] / D.E. Polonnikov. - M., 1983. - p. 141, Fig. 4.14.

12. Operational amplifiers and comparators. - M .: Publishing house "Dodeka-XXI", 2001, p. 259.

13. Nonlinear active correction in precision analog microcircuits: monograph / N.N. Prokopenko. - Rostov-on-Don: Publishing House of the North Caucasian Scientific Center of Higher Education, 2000. - 222 p.

14. Architecture and circuitry of high-speed operational amplifiers: monograph / N.N. Prokopenko, A.S. Budyakov. - Mines: Publishing House of SRUES, 2006. - 231 p.

Claims (3)

1. A broadband power amplifier with a low level of nonlinear distortion and noise, comprising an inverting output stage 1, the input of which is connected to the input of the device (2) and the input voltage source (3), a load circuit (4) connected to the output (5) of the device, associated with the output of the inverting output stage (1), characterized in that the input of the inverting output stage (1) is connected to the input (2) of the device and the input voltage source (3) through the first (6) additional resistor between the input (2) and the output (5) devices included after additionally connected second (7) and third (8) additional resistors, the common node of which (9) is connected to the input of the non-inverting correction stage (10), the current output of which (11) is connected to the input of the inverting output stage (1). 2. A broadband power amplifier with a low level of non-linear distortion and noise according to claim 1, characterized in that a voltage-current converter with a high input and high output resistances is used as a non-inverting correction stage (10). 3. A broadband power amplifier with a low level of non-linear distortion and noise according to claim 1, characterized in that a current amplifier with a low input and high output impedance is used as a non-inverting correction stage (10).

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