EP2111689A2

EP2111689A2 - Device for the low-distortion transformation, particularly amplification, of signals

Info

Publication number: EP2111689A2
Application number: EP07856144A
Authority: EP
Inventors: Jürgen Straussmann
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-12-22
Filing date: 2007-12-20
Publication date: 2009-10-28
Also published as: RU2009128211A; JP2010514285A; CA2673537A1; US7982649B2; CN101636912A; WO2008077387A2; US20100045375A1; WO2008077387A3

Abstract

The invention describes a device for the low-distortion transformation, particularly amplification, of signals. In one embodiment, the device comprises a digital-to-analog converter having adjustable reference voltages, to which an analog-to-digital converter having adjustable reference voltages may be connected upstream. In a further embodiment, the device has a unit, which predistorts a digitized signal, or a digital signal, corresponding to the transmission characteristic curve of the amplifier. In a further embodiment, the device has a unit, which equalizes a distorted digitized signal corresponding to the transmission characteristic curve of the amplifier stored in the unit. In yet a further embodiment, the device has a digital-to-analog converter operating on the basis of the summation of weighted currents.

Description

Device for low-distortion deformation, in particular

Amplification, of signals

The present invention relates to a device for low-distortion conversion, in particular amplification, of signals.

Electrical amplifiers are needed to amplify signals in terms of voltage, current or power. For this purpose, active components such as transistors or electron tubes are usually used, but also transformers can cause a gain.

Due to the non-linearity of the transfer characteristic of these components, however, nonlinear distortions, ie additional signal components that are not present in the original signal, are produced in the output signal. In order to reduce these non-linear distortions, the so-called negative feedback is used, in which part of the output signal is fed back out of phase by 180 ° to the input. However, this procedure has nalen considerable disadvantages, since it comes due to different maturities to new signal distortions.

The present invention has for its object to provide a device of the type described, with the distortions can be particularly largely reduced, without the need for this negative feedback.

According to a first embodiment of the invention, this object is achieved in that the device comprises a D / AWandler with adjustable reference voltages.

This embodiment of the invention relates to a device for the low-voltage distortion amplification of digitized analog signals, wherein the adjustment of the reference voltages of the D / A converter results in the required gain or the required level of the output voltage.

In a further embodiment of the invention, which is a device for the low-voltage, low-distortion amplification of analog signals, the device has a D / A converter upstream A / D converter with adjustable reference voltages. The setting of the reference voltages of the A / D converter and the D / A converter results in the required gain or the required level of the output voltage.

The embodiments described above make it possible to realize distortion-free amplifiers without the aid of negative feedbacks. A device which amplifies a signal which is either analog or digitally coded, for example in the PCM code, to an arbitrarily high voltage level, ie with an arbitrarily high gain V, with little distortion and without the aid of negative feedback, is according to the above explained embodiment, for example, constructed as follows:

An analog signal is first digitized by an A / D converter. The choice of the resolution (bit length) and the sampling rate (considering the Nyquist criterion) determines the quality, ie the proportion of nonlinear distortions, of the later output signal. An already digitally coded signal can be further processed directly. In the second step, the signal digitized in this way or the signal already present in digital form is switched to a D / A converter. This takes over the actual function of the voltage gain. By choosing the reference voltages + Uref and -Uref of the A / D converter and in particular the D / AWandlers one has a direct influence on the height of the output voltage and thus on the height of the signal amplification with a suitable design of the converter. It is possible, for example, to generate signal voltages of several 100 volts with the smallest possible non-linear signal components, with the exception of the signal components caused by the stepped output form, which, however, can be kept as small as desired by selecting a suitable resolution and sampling rate. Integrated D / A converters are generally designed for relatively low reference voltages (<+ -20 V). However, it is possible to build discrete transducers that are also high Can generate voltages. For this purpose, only the switches must be designed accordingly. Frequently, the sampling rate and resolution are not freely selectable, but determined by the system, eg CD standard 44.1 kHz sampling frequency and 16 bit resolution. In order to minimize the non-linear distortions arising in the conversion of a digital to an analog signal, a conventional D / A converter is extended by further devices.

The device is preferably designed so that the D / A converter can directly control a subsequent amplifier stage by appropriate design and selection of the reference voltages. The following amplifier stage can in this case represent the power output stage of an audio amplifier, and the D / A converter can provide the necessary control voltage or the control current directly by appropriate design.

The device can be used for example for analog signal conditioning (amplification) in an audio amplifier. It can convert digital audio signals into analog signals, such that the power output stage can be controlled directly in an audio amplifier.

In a further embodiment of the device according to the invention, the D / A converter further comprises:

Each bit has a group of four switches Sl to S4, an inversely operated R-2R-R ladder network, a generator for generating clock-synchronous rising and falling voltages, and one control logic per bit, which switches S1 to S4, the control logic via the switches Sl to S4 either Uref +, Uref, URampUp or URampDown at point 207 of the resistor 2R 211 sets in such a way that the value of one bit of two consecutive clocks is evaluated

is closed at an L / L sequence Sl,

when an L / H sequence S3 is closed,

is closed at an H / L sequence S4 and

is closed at a H / H sequence S2.

An analog signal, which is generated by a D / A converter from digital values, basically has steps with the width of the clock of the D / A converter. Such a signal additionally contains strong portions of the clock frequency and other higher frequencies. Therefore, one strives to smooth these steps as best as possible

(smoothing). For this purpose, filters are generally used which range from simple low-pass filters to higher-order filters. Some of these are also implemented as digital filters by digital signal processors. However, filters often have undesirable properties (phase shifts, overshoots, settling times, etc.).

By means of the device provided according to the invention, an automatic analogously generated signal is produced in the D / A converter

Smoothing (linear interpolation), which is the systemic, minimized by the conversion process generated nonlinear distortions, so that can be dispensed with further filtering measures. With the solution according to the invention, this can be realized with only one special D / A converter and without stepping between the sampled values.

D / A converters are usually realized with the aid of a resistor network. For example, the R-2R-R may be mentioned here. In this case, the branches with the 2R resistors are respectively connected to U + or U- via switches S1 and S2, corresponding to the value of the relevant bit. The switches are preferably realized with semiconductor switches.

This arrangement can be modified to realize an integrated smoothing as follows:

First, two ramp signals are generated by a generator in synchronism with the system clock (sampling clock), one rising from U to U + and one decreasing from U + to U-. Furthermore, two further switches S3 and S4 are inserted per 2R branch. Thus, one can apply to the respective 2R resistor either U + (Sl), U- (S2), a rising ramp U- to U + (S3) or a ramp from U + to U- (S4).

The switches Sl to S4 are controlled by a control logic as follows:

Assuming that the binary input signal was previously L, then as in the conventional D / A converter, the switch Sl closed. At point 207 of the 2R resistor is U-. If the input signal changes to H, Sl is opened, but not closed as before S2, but S3. This places the Ramp rising from U to U + to 2R. At the end of the clock, the voltage reaches 2R (207) U +.

If the input signal also remains at H in the next cycle, S3 is opened and S2 is closed. At 2R (207) then fixed at U +. However, if the signal changes to L, S3 is opened and S4 is closed and the ramp from U + to U is connected to 2R (207). Thus, the voltage at the end of the clock has fallen back to U-.

According to this principle, the control logic activates the switches S1 to S4 of all stages of the D / A converter. The result is an output voltage of the D / A converter, as shown in the following Figure 5. Due to different ramp shapes, the type of "sanding" can be varied.

A further improvement of the smoothing can be achieved as follows:

The input values of the D / A converter are changed as follows:

DAin (t + 1) = N (t) + (N (t + 1) -N (t)) / 2

N are the original digital values.

This can be realized by a microprocessor which is placed in front of the D / A converter and this calculation performs. In the following Figure 5, the effect of the two smoothing functions compared to the conventional D / A converter is shown. The solid line shows the simple smoothing, while the dot-dash line shows the improved smoothing.

Further optimization of the smoothing can be achieved by changing the shape of the ramp voltage. Instead of a linear ramp, two "bulbous" ramps are used, one concave and one convex, thus four ramps in total, two for UP and two for DOWN, and the next value is considered when outputting a value Value and the previous value smaller than the distance of the current and the next value, the convex ramp is used, otherwise the concave one, in the other case the situation reverses.This type of procedure makes the resulting analogue signal even smoother, but increases the effort.

D / A converters of the type described above are ideal for implementation as integrated circuits. They are also characterized by low noise of the output signal, since the current flow in the resistors 2R in the switching operations does not change abruptly and thus disturbances are avoided by current jumps.

The device described above thus relates to one in which the ramp voltage increases or decreases linearly. In another embodiment, the ramp voltage has a shape deviating from the linear shape. Preferably, there is another means for changing the digital input values prior to output to the D / A converter such that the value for the clock T + 1 is the average between the value for the clock T + 1 and that of the clock T results.

As explained above, the invention further proposes a device in which more than two ramps for further smoothing optimization are generated in the D / A converter, which can be connected to the points (207) of the 2R resistors via corresponding additional switches.

The digital data can be digitized music data. The device can be used as an D / A converter in an integrated circuit (IC).

If it is not possible to circumvent the use of active components, such as transistors or electron tubes, in order to achieve a required power gain for driving a load, additional signal components (non-linear distortions) which are not present in the original signal are generated due to the non-linear transfer characteristic of these components. These distortions are reduced according to the prior art by negative feedback measures. By means of the further solution according to the invention described below, a substantial reduction of the distortions due to nonlinearities can be effected. This solution relates to a device for reducing distortions in electrical amplifiers caused by non-linearities in the active devices, comprising:

A unit which predistorted a digitized signal or a digital signal according to the transfer characteristic of an amplifier,

a unit in which the transfer characteristic or its inversion is stored, and

a D / A converter, which generates an analog signal from the digital predistorted signal and drives the amplifier with this signal, wherein the distortion of the amplifier is compensated by the predistortion of the input signal, so that overall a low-distortion gain despite the non-linearity of the amplifier results.

The inventively designed device can process both analog and digitized signals. An analog signal is digitized by an A / D converter before further processing. The digitized values are fed to a unit which, knowing the non-linearity of the transfer characteristic of the amplifier system to be linearized, alters these values so as to give a low-distortion output signal after later passing through the non-linear system. For this purpose, the input values must be multiplied by the inverse transfer function. This causes a digital predistortion of the signal. Subsequently, the thus pre-distorted digital signal is output to a D / A converter whose output signal in turn directly controls the amplifier stage to be linearized. With a suitable design of the D / A converter, it can fulfill any possible requirement for controlling the amplifier stage, for example by correspondingly high reference voltages + Uref and -Uref and high output voltages for the direct control of the grid of an electron tube. This signal is amplified by the active device, producing nonlinear distortions. Due to the fact that the signal was already predistorted by the D / A converter with the inverse transfer function, both distortions compensate each other, so that overall an undistorted signal is set at the output of the amplifier system.

This device requires the knowledge of the non-linearity of the amplifier, which is stored as an inverse function. If the non-linear behavior changes with time and / or temperature, this device no longer works optimally.

To remedy these problems, in a further embodiment of the invention, the device additionally has a unit for the metrological evaluation of the output signal of the amplifier, a unit for processing the data and a unit which is suitable for permanently storing the transfer characteristic or its inversion, on the other hand, to allow for changes in the individual values during operation, with each

Output of a new digital value the unit of measurement technical evaluation, the output signal is indexed, passed on to the unit for processing the data, which then performs a nominal / actual comparison between the values and corrects the respective value of the transfer characteristic in the event of deviations, whereby the

Function of the device is always guaranteed even with changes in the characteristic curve within the amplifier (adaptive behavior).

The unit which allows changes of the individual values is preferably initially initialized with the function y = x, so that, after a short time due to the functioning of the device, the characteristic curve of the amplifier or the inverse thereof automatically sets.

The device described above offers the advantage of automatically adapting changes in the transfer characteristic (adaptive behavior). Optionally, it is also possible to dispense with recording the transfer function for the first time since, after a certain learning phase, the device itself adjusts itself to minimal distortion, ie it autonomously "learns" the transfer characteristic of the amplifier.

For this purpose, the device is supplemented by other facilities. A measuring device measures the output signal every time a new value is output by the D / A converter. Another device compares this digitized actual value with the digitized target value, i. the undistorted digital input signal. The current inverse

Transfer characteristic is in the serving unit managed. It is initialized at initial startup with an initial transfer characteristic, such as the function y = x. If the further device detects a deviation between the digital set value and the measured actual value, it corrects the relevant value in the inverse transfer characteristic accordingly. The correction can take place to different degrees; it takes a correspondingly long time until the "correct" correction function, which corresponds to the inverse transfer function, sets in total.

The two aforementioned devices use a predistortion of the input signal of the non-linear amplifier system. Alternatively, the output signal of a non-linear amplifier system can also be subsequently corrected, so that the nonlinear distortions are reduced. According to this solution, the invention proposes a device comprising:

An A / D converter that converts the analog output of the amplifier into a digital signal,

a unit which equalizes the distorted digitized signal according to the transmission characteristic of the amplifier stored in a unit and, if necessary, makes it available for digital further processing,

a unit in which the transfer characteristic or its inversion is stored, and a D / A converter that generates an analog signal from the digital equalized signal,

wherein the equalization of the output signal by means of the stored in the unit transfer characteristic of the amplifier or its inverse, the nonlinear distortions generated in the amplifier are compensated, so that the overall results in a low-distortion gain despite the non-linearity of the amplifier.

In this embodiment, the analog signal to be amplified is amplified by a non-linear amplifier. The output signal contains additional distortions due to the non-linearity of the amplifier system. This signal is digitized by the A / D converter and multiplied by an equalizer unit with the inverse transfer characteristic. At the output you get the low-distortion signal in digital form for possibly digital further processing. This finally passes through a D / A converter, which generates the signal in analog form, wherein the signal level on the reference inputs of the D / A converter are arbitrarily adjustable.

If the inverse transfer characteristic curve is to be determined by the device itself and / or adapt itself to changes (adaptive behavior), the device described above must be supplemented by further devices. A measuring device measures the input signal. Another device compares the digitized actual value that results after passing through the input signal through the amplifier system, the A / D converter and the Equalizer is set at the output of the unit, with the digital setpoint, the undistorted digital input signal. The current inverse transfer characteristic is managed in the unit. It is initialized at initial startup with an initial transfer characteristic, such as the function y = x. If the unit detects a deviation between the digital reference value and the resulting actual value, it corrects the corresponding value in the inverse transfer characteristic accordingly. The correction can be made different degrees. It takes a correspondingly long time until the "correct" correction function, which corresponds to the inverse transfer function, sets in total.

In a further embodiment of the invention, therefore, the device additionally has a unit for metrological evaluation of the input signal of the amplifier, a unit for processing the data and a unit which is suitable for permanently storing the transfer characteristic or its inversion, on the one hand, and changes, on the other hand the individual values during operation by the unit, wherein the input signal of the amplifier is metrologically detected by the unit and passed to the unit for processing the data, which then between the values of a target / actual

Performs comparison and corrected in case of deviations the relevant value of the transfer characteristic stored in the unit for storing, whereby the function of the device is always guaranteed even with changes in the characteristic within the amplifier (adaptive behavior). In this case, the unit for storing is preferably initially initialized with the function y = x, whereby the characteristic curve of the amplifier or the inverse of it automatically sets itself after a short time due to the mode of operation of the device.

Preferably, the non-linear amplifier is a general amplifier for voltage, current or power amplification. In particular, the non-linear amplifier is the power output stage of an audio amplifier. However, it may also be a preamplifier stage of an audio amplifier.

When using the device in an audio amplifier, the D / A converter preferably generates a signal in such a way that the analog output stage of the audio amplifier can be controlled directly.

The above object is further achieved in a device for low-distortion conversion, in particular amplification, of signals according to the invention in that a D / A converter, which operates on the basis of the summation of weighted currents, the summed individual streams directly to a load gives off, which is delivered to the load a corresponding performance.

In this case, the device preferably serves to amplify the power of digital signals. The provision of the individual component streams can take place via individual current sources or also through conductor networks. Such a device can be designed as a low-distortion power amplifier, in particular for audio application.

Power amplifiers are usually realized with the aid of active components, such as transistors or electron tubes. The resulting non-linear distortions can be reduced according to the prior art by countercoupling measures. The inventively embodied device is capable of power amplifying digital signals, with the least possible distortion, without the use of negative feedback measures. For this purpose, a D / A converter is used, which operates on the basis of weighted currents. These can be generated either via ladder networks or through switchable weighted constant current sources. The individual partial currents are switched directly to the load R and cause there directly a power output P = I ² * R. The ratio of the partial currents is always 1: 2: 4: 8: .... The desired amplifier power can be over the absolute height of Partial streams are set.

The invention will be explained below with reference to exemplary embodiments in conjunction with the drawings. Show it:

FIG. 1 shows a block diagram of a first embodiment of a device for the low-distortion amplification of signals; FIG. 2 shows the structure of a conventional D / A converter with an inversely operated R2R ladder network;

Figure 3 shows the structure of a D / A converter according to the invention with integrated analog smoothing;

FIG. 4 shows the mode of operation of the D / A converter of FIG. 3 for one bit;

Figure 5 shows the effect of smoothing on an input signal;

FIG. 6 shows a block diagram of a further embodiment of a device for low-distortion amplification of signals;

FIG. 7 shows a block diagram of yet another embodiment of a device for the low-distortion amplification of signals;

FIG. 8 shows a block diagram of a further embodiment of a device for the low-distortion amplification of signals;

FIG. 9 shows a block diagram of a further embodiment of a device for the low-distortion amplification of signals; and

FIG. 10 shows a circuit diagram of a device for the amplification of a digital signal.

FIG. 1 shows the structure of a device for low-distortion voltage amplification of analog 100 or digitized 108 signals, without the need for negative feedback. The analog signal 100 is converted by means of the A / D converter 101 into a digital signal 109 and then converted back into an analog signal 107 of arbitrary height by means of the D / A converter 102, the gain being determined by selecting the suitable reference voltages 102 and 103 becomes. An optionally digitized signal is also converted by the D / A converter 102 into an analog signal of any height.

Figure 2 shows the structure of a conventional D / A converter with an inverse R2R ladder network. According to the respective bit value, the switches Sl and S2 switch the upper resistors 2R to either Uref + or Uref-.

FIG. 3 shows the construction of a D / A converter with integrated analog smoothing designed according to the invention. A ramp generator 200 generates in each case sampling synchronously an ascending 201 and a falling 202 ramp. For each bit in addition to the usual switches Sl and S2, two additional switches S3 203 and S4 204 are present, by means of which, depending on the bit sequence, controlled by a control logic 206, either one of the reference voltages or one of the ramps to the relevant 2R resistor 211 are placed can. Hereby one achieves in the consequence an optimal smoothing. Figure 4 shows the operation of this D / A converter for a bit. Shown are the isochronously generated ramps RampUp 201 and RampDown 202, the input signal 212, the function of the switches S1 to S4 as a function of the input signal, and the voltage applied to the resistor 2R 211 at the point 207.

Figure 5 shows the effect of smoothing on an input signal. The dashed line shows the output voltage of a D / A converter without smoothing, the bold solid line 209, the output voltage of the inventive D / AW with smoothing and the dotted line 210, the output voltage of the inventive D / A converter with improved smoothing.

FIG. 6 shows the structure and operation of a distortion mitigation device that results in a nonlinear amplifier system 305. The analog input signal 301 is digitized by means of the A / D converter 302 (303). An alternative digital input signal 300, as well as the digitized analog signal 303, is pre-distorted in unit 304 in consideration of the inverse transfer characteristic 306 of the non-linear amplifier system 305. Predistorted, it is converted back to an analog signal by a D / A converter 308 (309), which serves as an input to the amplifier 305. The amplifier amplifies the signal 309 non-linearly, resulting overall in a linear course for the output signal 310, since pre-emphasis and non-linear distortion compensate each other. FIG. 7 shows the construction of another device for reducing distortions arising in a nonlinear amplifier system 305. The construction is similar to that of FIG. 6. While in the apparatus of FIG. 6 the inverse transfer characteristic is firmly anchored in 306, it can be corrected and / or determined by the apparatus of FIG. 7, thus providing optimal low distortion under all operating conditions Operation is guaranteed. For this purpose, the output signal 310 of the amplifier system 305 is measured via the unit 311. This measured value 312, which represents the actual value, is compared with the desired value 303 by the unit 313. Based on the deviations, the relevant point of the inverse transfer characteristic 314 is corrected.

FIG. 8 shows the structure and mode of operation of another device for reducing distortions arising in a non-linear amplifier system 321. In contrast to the embodiment of FIG. 6, the analog input signal 320 is first amplified by the non-linear amplifier 321. The amplified distorted signal 322 is digitized (303) by means of the A / D converter 323 and equalized in the unit 324 due to the inverse transfer characteristic 325 of the non-linear amplifier system 321. This undistorted digital signal 326 is converted by the D / A converter 327 into an undistorted analog signal of arbitrary voltage level, adjustable by selecting the appropriate reference voltages of the D / A converter 327.

FIG. 9 shows the structure of a further device for reducing distortions which are in a non-linear manner Amplifier system 321 arise. The construction is similar to that of FIG. 8. While in the device according to FIG. 8 the inverse transfer characteristic is firmly anchored in 325, it can be corrected and / or determined in the device according to FIG. 9, whereby under all operating conditions optimal distortion-free operation is guaranteed. For this purpose, the input 330 of the amplifier system 321 is measured via the unit 330. This measured value 331, which represents the desired value, is compared with the actual value 326 by the unit 329. Based on the deviations, the relevant point of the inverse transfer characteristic 328 is corrected.

FIG. 10 shows a device for the power amplification of a digital signal, carried out here by a D / A converter with weighted current sources.

In addition, reference should generally be made to the following. The power output stage mentioned above may also be the output stage of a video amplifier. The

Device can therefore also be used for analog signal conditioning (preamplification) in a video amplifier. This also applies to an amplifier of measurement and control technology. The device can generally be used for general signal amplification.

The device can also convert digital image data (video signals) into analog signals in such a way that the power output stage in a video amplifier can be directly controlled. This also applies to digitized signals an amplifier of measurement and control technology.

The digital signals may be digitized image data (video signals). The digitized data may be general digitized physical data (measurement data).

The amplifier can be a video amplifier or an amplifier of the measurement, control and regulation technology.

The D / A converter can also generate a signal in such a way that the analogue end or pre-stage of a video amplifier or the analogue end or pre-stage of an amplifier of the measuring and control technology can be directly controlled.

The low distortion conversion apparatus having a D / A converter operating based on the summation of weighted currents can be used for video applications or for measurement and control technology applications, for example.

Claims

claims

1. A device for low-distortion conversion, in particular amplification, of signals, characterized in that it comprises a D / A converter (102) with adjustable reference voltages (105, 106).

2. Apparatus according to claim 1, characterized in that it comprises a D / A converter (102) upstream A / D converter (101) with adjustable reference voltages 8103, 104).

3. Apparatus according to claim 1 or 2, characterized in that the D / A converter (102) directly controls a subsequent amplifier stage.

4. The device according to claim 3, characterized in that the subsequent amplifier stage represents the power output stage of an audio amplifier and that the D / A converter (102) directly provides the necessary control voltage or the control current by appropriate design.

5. Device according to one of the preceding claims, characterized in that it is used for analog signal processing (preamplification) in an audio amplifier.

6. Device according to one of the preceding claims, characterized in that it converts digital audio signals into analog signals in such a way that the power output stage in an audio amplifier is directly controllable.

7. Device according to one of the preceding claims, characterized in that the D / A converter further comprises:

each bit a group of four switches Sl to S4, an inversely operated R-2R-R ladder network, a generator (210) for generating isochronous rising (201) and falling (202) voltages and bit control logic (206) for each bit which drives the switches S1 to S4, the control logic (206) applying via the switches S1 to S4 either Uref +, Uref, URampUp (201) or URampDown (202) to a point (207) resistor 2R in such a way that the value of one bit of two consecutive clocks is evaluated, wherein

- is closed at an L / L sequence Sl,

is closed at an L / H sequence S3, - is closed at an H / L sequence S4 and

- is closed at a H / H sequence S2.

8. The device according to claim 7, characterized in that the ramp voltage increases linearly (201) or falls (202).

9. Apparatus according to claim 7, characterized in that the ramp voltage has a shape deviating from the linear shape.

10. Device according to one of claims 7 to 9, characterized in that it comprises a further device which changes the digital input values prior to output to the D / A converter, such that the value for the clock T + l from the mean between the value for the clock T + l and that of the clock T results.

11. Device according to one of claims 7 to 10, characterized in that in the D / A converter more than two ramps for further smoothing optimization are generated and via corresponding additional switch to the points (207) of the 2R resistors (211) be placed.

12. Device according to one of claims 7 to 11, character- ized in that it is the digital signals to digitized music data.

13. Device according to one of claims 7 to 12, characterized in that it is used in an integrated circuit (IC) as a D / A converter use.

14. A device for low-distortion conversion, in particular amplification, of signals, characterized in that it comprises the following components:

a unit (304) predistorting a digitized signal (303) and a digital signal (300) according to the transfer characteristic of an amplifier (305),

a unit (306) in which the transfer characteristic or its inversion is stored, and

a D / A converter (308) which generates an analog signal from the digital predistorted signal (30/9 and drives the amplifier (305) with this signal,

wherein the distortion of the amplifier (305) is compensated by the predistortion of the input signal, so that overall a low-distortion gain results despite the non-linearity of the amplifier (305).

15. The apparatus according to claim 14, characterized in that it additionally comprises a unit (311) for metrological evaluation of the output signal (310) of the amplifier (311), a unit for processing the data (303) and (312) as well as a unit (314) which is suitable for permanently storing the transfer characteristic or its inversion on the one hand, on the other hand, to permit changes in the individual values during operation by the unit (313), with each output of a new digital value (300) or (303) the unit (311) measuring the output signal, to which

Unit (313) passes on, which then performs a target / actual comparison between the values (300) and (303) and (312) and in case of deviations the respective value of the transfer characteristic, which is stored in the unit (314) corrected , whereby the function of the device is always ensured even with changes in the characteristic within the amplifier (311).

16. The device according to claim 15, characterized in that the unit (314) is first initialized with the function y = x and after a short time due to the operation of the device, the characteristic of the amplifier (305) or the Inver sen thereof independently established.

17. Device according to one of claims 14 to 16, characterized in that it is the non-linear amplifier (305) or (310) is a general amplifier for voltage, current or power amplification.

18. Device according to one of claims 14 to 17, characterized in that it is the non-linear amplifier (305) or (310) is the power output stage of an audio amplifier.

19. Device according to one of claims 14 to 17, characterized in that it is the non-linear amplifier (305) or (310) is a Vorverstärerstufe an audio amplifier.

20. Device according to one of claims 14 to 19, characterized in that the D / A converter (327) generates a signal (328) in such a way that the analog output stage of the audio amplifier can be controlled directly.

21. A device for low-distortion conversion, in particular amplification, of signals, characterized in that it comprises the following constituents:

an A / D converter (323) that converts the analog output signal (322) of an amplifier (321) into a digital signal (332);

a unit (324) for equalizing the distorted digitized signal (332) according to the transfer characteristic of the amplifier (305) stored in a unit (325) and, if necessary, providing it for further digital processing; a unit (325) in which the transfer characteristic or its inversion is stored; and

a D / A converter (327) that generates an analog signal (328) from the digital equalized signal (326),

wherein the equalization of the output signal (322) by means of the transfer characteristic of the amplifier (321) or its inverse stored in the unit (325) compensates for the non-linear distortions generated in the amplifier, so that, overall, a low-distortion gain is achieved Nonlinearity of the amplifier (321) results.

22. The apparatus according to claim 21, characterized in that it additionally comprises a unit (330) for the metrological evaluation of the input signal

(320) of the amplifier (321), a unit (329) for processing the data (331) and (326), and a unit (328) which is capable of permanently storing the transfer characteristic or its inversion, on the one hand, and changes of the individual values during operation by the unit (329), whereby the input signal of the amplifier (321) is detected by the unit (330) and forwarded to the unit (329), which then between the values (331 ) and (329) performs a target / actual comparison and in the event of deviations, the relevant value of the transfer characteristic stored in the unit (328) is corrected, whereby the function of the device always remains ensured even when the characteristic changes within the amplifier (321).

23. The device according to claim 22, characterized in that the unit (328) is first initialized with the function y = x and after a short time due to the operation of the device, the characteristic of the amplifier (321) or the Inverse sen of which independently stops.

24. The apparatus of claim 22 or 23, characterized in that it is the non-linear amplifier is a general amplifier for voltage, current or power amplification.

25. Device according to one of claims 22 to 24, characterized in that it is the non-linear amplifier to the power output stage of an audio amplifier.

26. Device according to one of claims 22 to 25, characterized in that it is the non-linear amplifier to a preamplifier stage of an audio amplifier.

27. The device according to one of claims 22 to 26, characterized in that the D / A converter generates a signal in such a way that the analog output stage of the audio amplifier can be controlled directly.

A low-distortion conversion apparatus, in particular amplification, of signals, characterized in that it comprises a D / A converter which operates on the basis of the summation of weighted currents and outputs the summed individual currents directly to a load, thereby applying to the load R a corresponding power is delivered.

29. The device according to claim 28, characterized in that it serves as a low-distortion power amplifier.

30. Device according to claim 28, characterized in that it serves as a low-distortion power amplifier for audio applications.