HK1092603B - Amplifier system and method - Google Patents

Description

Amplifier system and method

Technical Field

The present invention relates generally to amplifier systems and methods, and more particularly to amplifier systems and methods suitable for use in the field of high fidelity audio amplifiers.

Background

High quality sound systems require amplifiers that produce good sound quality. Sound quality is not easily measurable and an amplifier with good physical characteristics (e.g., wide frequency response at low and high frequencies, low phase shift, and low distortion) does not necessarily produce sound of good quality. The reason for this may be due to errors or distortions that are not apparent when studying the physical characteristics of the amplifier. These distortions can be reduced by applying an overall negative feedback.

For audio applications it is believed that amplifiers without feedback may have good characteristics that are satisfactory for sound. However, amplifiers without feedback generally do not have good measurement characteristics (e.g., Total Harmonic Distortion (THD) measurements) compared to amplifiers that utilize feedback.

Therefore, there is a need for an amplifier with better measurement characteristics and thus better performance, regardless of whether feedback is applied or not.

Disclosure of Invention

In general, the present invention provides an amplifier system and method in which errors in two or more amplifiers in the system are cancelled by subtraction.

According to a first aspect of the present invention, there is provided an amplifier system comprising:

a first amplifier arranged to receive an input signal;

a second amplifier arranged to receive a portion of the input signal, the second amplifier having an output signal; and

a first voltage divider arranged to receive the output signal of the second amplifier and feed a portion of the output signal to the first amplifier;

wherein the first amplifier is arranged to subtract the portion of the output signal of the second amplifier from the input signal to produce a difference signal that is amplifiable by the first amplifier.

According to a second aspect, there is provided an audio amplifier system comprising an amplifier system as defined above.

According to a third aspect of the present invention, there is provided a method of amplifying a signal, comprising:

applying an input signal to a first amplifier;

applying a portion of the input signal to a second amplifier, the second amplifier having an output signal;

applying the output signal of the second amplifier to a first voltage divider;

applying a portion of the output signal to the first amplifier; and

subtracting the portion of the output signal of the second amplifier from the input signal in the first amplifier to produce a difference signal that is amplifiable by the first amplifier.

Drawings

Preferred features of the invention will now be described, for illustrative purposes only, with reference to the following drawings, in which:

FIG. 1 is a schematic circuit diagram of an amplifier circuit according to one embodiment of the invention;

FIG. 2a shows the frequency response of an amplifier circuit taken at the output of amplifier 20 in the circuit of FIG. 1;

FIG. 2b shows the frequency response of an amplifier taken at the output of amplifier 10 in the circuit of FIG. 1;

FIG. 3a further illustrates the phase shift of the amplifier circuit taken at the output of amplifier 20 in the circuit of FIG. 1;

FIG. 3b further illustrates the phase shift of the amplifier taken at the output of amplifier 10 in the circuit of FIG. 1;

FIG. 4a is a graph of the spectrum of the output signal of amplifier 20 in the circuit of FIG. 1 with an input of 1 kHz;

FIG. 4b is a graph of the spectrum of the output signal of amplifier 10 in the circuit of FIG. 1 with an input of 1 kHz;

fig. 5 is a schematic circuit diagram of an amplifier circuit according to a second embodiment of the present invention;

fig. 6 is a schematic circuit diagram of an amplifier circuit according to a third embodiment of the present invention;

fig. 7 is a schematic circuit diagram of an amplifier circuit according to a fourth embodiment of the present invention; and is

Fig. 8 is a schematic circuit diagram of an amplifier circuit according to a fifth embodiment of the present invention.

Detailed Description

FIG. 1 showsAn amplifier circuit according to one embodiment of the present invention is shown. The circuit includes two identical amplifiers: a main amplifier (X1)10 and a second amplifier (X2) 20. Both amplifiers have the gain G required by the whole system_VTwice as much. Since the amplifiers are identical, they will produce a similar error E during amplification. Ideally, the same operating conditions, such as the same supply voltage, the same input voltage, and the same load impedance, are applied to the amplifiers 10 and 20.

In the system of fig. 1, the input signal V_inIs applied to a first point (point 1) and then to the positive input of the main amplifier 10. The input signal is also applied to a first end of a first resistor R1, the other end of the first resistor R1 being connected to a first end of a second resistor R2. The other end of the second resistor R2 is connected to system ground. First and second resistors R1 and R2 form a voltage divider, the junction of which is connected to the positive input of the second amplifier 20. The negative input of the second amplifier 20 is connected to system ground at point 2.

The output of the second amplifier 20 is connected at point 3 to a first end of a third resistor R3, the other end of the third resistor R3 being connected to a first end of a fourth resistor R4. A second end of the fourth resistor R4 is connected to system ground.

The junction of the third and fourth resistors R3 and R4, referred to as point 4, is connected to the negative input 9 of the main amplifier 10. The output of the main amplifier 10 is connected to one end of a load, which may be, for example, another amplifier such as a power amplifier, in which case the load is a resistive element to ground, or another element such as a speaker. The other end of the load is connected to system ground. The voltage across the load constitutes the output of the amplifier circuit.

Preferably, the first and second resistors R1 and R2 are identical, then the signal at point 5 (the positive input of the second amplifier 20) will be half the input signal at point 1. Therefore, if

R₁＝R₂Then, then

.................................(1)

The voltage at point 3 (the output of the second amplifier 20) is given by:

where E is the error produced by X2

Substitution equation (1)

V₃＝G_VV_in+E .................................(2)

Preferably, the third and fourth resistors R3 and R4 are high precision resistors whose values have the following relationship:

.................................(3)

and, if R3+ R4 ═ R_loadThen the load of amplifiers 10 and 20 is equal, which is an optimum condition but is not necessary for the invention to function. Ideally, such load conditions should be achieved to achieve optimal results. However, the present invention will work even if there is a deviation from this load condition.

The voltage at the output of the voltage divider formed by the third and fourth resistors R3 and R4 is given by:

substituting into equation (2) and equation (3)

.................................(4)

This voltage V4 is applied to the negative input of the main amplifier 10 at point 9, and the voltage at point 9 can be expressed as follows:

.................................(5)

the main amplifier 10 is connected at a positive input at point 8 to the system input at point 1. Thus, the voltage at point 8 can be expressed as follows:

V8＝V_in .................................(6)

the voltage at the output of the main amplifier 10 at point 6 can be given by:

V6＝2×G_V(V8-V9)+E

if V8 and V9 in the above equation are substituted with equations (6) and (5), respectively:

V₆＝G_VV_in .................................(7)

it can be seen that the error E produced during amplification is cancelled, leaving the output V of the amplifier circuit at point 7_outComprises the following steps:

V_out＝G_VV_in

an alternative representation of these equations is set forth below. In this alternative representation, the errors generated in amplifier 10 and amplifier 20 are distinguished by naming them as E1 and E2, respectively. In the present embodiment, it is also shown that R1 ═ R2 is a condition that the output levels of both amplifiers 10 and 20 are the same, and thus is also a condition that the errors from amplifiers 10 and 20 are the same. In general, the input amplitude to amplifier 20 should be half the input amplitude to amplifier 10.

Signal at point 5 (positive input of second amplifier 20)

Let A1 be the attenuation of the voltage divider formed by resistors R1 and R2, i.e.

Then V₅＝A₁V_in .................................(1)

Let G be the gain of a single amplifier (rather than the entire system), then

V₃＝G(V₅-V₂)+E₂Substitution equation (1)

V₃＝A₁GV_in+E₂ .................................(2)

Wherein E is₂Is an error generated in the second amplifier 20, and V₂＝0。

The output terminal voltage of the voltage divider formed by the third and fourth resistors R3 and R4 can be given by:

let A₂Attenuation of the voltage divider formed by resistors R3 and R4, i.e.

Then V₄＝A₂V₃

This voltage V₄Applied to the negative input of the main amplifier 10 at point 9, the voltage at point 9 can be expressed as follows:

V₉＝V₄＝A₂A₁GV_in+A₂E₂ .................................(3)

the voltage at the output of the main amplifier 10 at point 6 may be given by:

V₆＝G(V₈-V₉)+E₁in which E₁Is an error generated in the first amplifier 10 and thus

V₆＝G(V_in-A₂A₁GV_in-A₂E₂)+E₁

＝G(1-A₂A₁G)V_in-A₂GE₂+E₁ .................................(4)

In order to eliminate the error term(s),

-A₂GE₂+E₁＝0

if the errors generated in both amplifiers 10 and 20 are the same, i.e. E₁＝E₂Then, then

E₁(1-A₂G)＝0

In order to make the errors from both amplifiers 10 and 20 the same, i.e. E₁＝E₂The operating conditions of both amplifiers 10 and 20 should be the same. One consideration is that the output levels from both amplifiers 10 and 20 should be the same to make the operating conditions the same because they have the same gain and they are the same.

Therefore, one way to check is to set the output of the first amplifier 10 equal to the output of the second amplifier 20. Therefore, the temperature of the molten metal is controlled,

V₃＝V₆

A₁GV_in+E₂＝G(1-A₂A₁G)V_in-A₂GE₂+E₁derived from equations (2) and (4)

Since the magnitude of the error is much smaller than the amplified output signal, ignoring the error term,

A₁GV_in＝G(1-A₂A₁G)V_in

due to the fact that

Then A is₁＝1-A₁

This means that for this example, R₁＝R₂Is a necessary condition for two amplifiers to have practically the same output level and thus the same error. It should be noted, however, that even a slight deviation from this condition, namely R₁Is not equal to R₂The system incorporating the invention should still function. Under this condition, the error at the output will be higher. This has been confirmed by simulations.

Use ofAndfrom the equation (4),

if the errors are equal and cancel each other out, then

If we make the gain of the whole system to be G_V(as before), then

And V₆＝G_VV_in

Thus, the output is an input signal with a gain G_VWithout error.

Figure 2a shows the frequency response of an amplifier circuit taken at the output of amplifier 20 in the circuit of figure 1, which gives a bandwidth of 1.373MHz at the-3 db point. Since amplifiers 10 and 20 are identical and operate under similar conditions, amplifier 20 alone may be considered a standard amplifier that does not incorporate the present invention.

Figure 2b shows the frequency response of an amplifier taken at the output of amplifier 10 in the circuit of figure 1 according to one embodiment of the present invention which gives a bandwidth of 3.234MHz at the-3 db point.

Fig. 3a shows a phase shift of an amplifier circuit taken at the output of amplifier 20 in the circuit of fig. 1. A phase deviation of-5.252 degrees at 100kHz is shown.

Fig. 3b shows the phase shift of the amplifier taken at the output of the amplifier 10 in the circuit of fig. 1. The phase deviation of-2.082 degrees at 100kHz is shown.

It is noted that 20kHz is a typical upper audio frequency limit.

Fig. 4a is a spectrum plot of the output signal of amplifier 20 in the circuit of fig. 1 when the input is 1kHz, and fig. 4b is a spectrum plot of the output signal of amplifier 10 in the circuit of fig. 1 when the input is 1 kHz.

Fig. 4a and 4b show the improvement of Total Harmonic Distortion (THD) more clearly. As shown in these figures, the THD + noise from amplifier 20 is 0.9415%, while that of amplifier 10 is 0.0367%. These digital values will vary depending on the input level set by the emulation.

Fig. 5 shows an amplifier circuit according to a second embodiment of the invention. The circuit includes two identical amplifiers: a main amplifier (X1)10 and a second amplifier (X2) 20. Both amplifiers have the gain G required by the whole system_VTwice as much. Since the amplifiers are identical, they will produce a similar error E during amplification. Ideally, the same operating conditions, such as the same supply voltage, the same input voltage, and the same load impedance, are applied to the amplifiers 10 and 20.

In the system of fig. 5, the input signal V_inIs applied to a first point (point 1) and then to the positive input of the main amplifier 10. The input signal is also applied to the positive input of the second amplifier 20 at half the level. The negative input of the second amplifier 20 is connected to system ground at point 2.

The output of the second amplifier 20 is connected at point 3 to a first end of a first resistor R3, the other end of the first resistor R3 being connected to a first end of a second resistor R4. A second end of the second resistor R4 is connected to system ground.

The junction of the first and second resistors R3 and R4, referred to as point 4, is connected to the negative input 9 of the main amplifier 10. The output of the main amplifier 10 is connected to one end of a load, which may be, for example, another amplifier such as a power amplifier, in which case the load is a resistive element to ground, or another element such as a speaker. The other end of the load is connected to system ground. The voltage across the load constitutes the output of the amplifier circuit.

Operation of the circuit of fig. 5 in combination with the aboveThe same as described for fig. 1, the only difference being that the voltage divider consisting of R1 and R2 present in the circuit of fig. 1 has been removed from the circuit of fig. 5. However, for the embodiment of fig. 5 to work optimally, the magnitude of the input to amplifier 20 should be half that of the input to amplifier 10. In the present embodiment, input V_inIs applied to an amplifier 10 of the same but of half V in amplitude_inThe input of/2 is applied to amplifier 20. These inputs may be from a source, such as a digital source with a digital-to-analog converter used to obtain the above configuration.

Fig. 6 shows an amplifier circuit according to a third embodiment of the present invention. The circuit includes two identical amplifiers: a main amplifier (X1)10 and a second amplifier (X2) 20. Both amplifiers have the gain G required by the whole system_VTwice as much. Since the amplifiers are identical, they will produce a similar error E during amplification. Ideally, the same operating conditions, such as the same supply voltage, the same input voltage, and the same load impedance, are applied to the amplifiers 10 and 20.

In the system of fig. 6, the input signal is applied to a first point (point 1) and then to a voltage divider formed by two resistors R5 and R6. The junction of the voltage divider (point 8) is connected to the positive input of the main amplifier 10. The end of resistor R6 not connected to resistor R5 is connected to system ground. The input signal is applied to the end of resistor R5 that is not connected to resistor R6. The input signal is also applied to a first end of another resistor R1, the other end of the resistor R1 being connected to a first end of another resistor R2. The other end of the resistor R2 is connected to system ground. Resistors R1 and R2 form a voltage divider, the junction of which (point 5) is connected to the positive input of the second amplifier 20. The negative input of the second amplifier 20 is connected to system ground at point 2.

The values of R1, R2, R5, and R6 are chosen such that the voltage applied to the positive input of amplifier 20 (point 5) is half the voltage applied to the positive input of amplifier 10.

The output of the second amplifier 20 is connected at point 3 to a first terminal of a further resistor R3, the other terminal of the further resistor R3 being connected to a first terminal of a further resistor R4. The second end of the resistor R4 is connected to system ground.

The junction of the resistors R3 and R4, referred to as point 4, is connected to the negative input 9 of the main amplifier 10. The output of the main amplifier 10 is connected to one end of a load, which may be, for example, another amplifier such as a power amplifier, in which case the load is a resistive element to ground, or another element such as a speaker. The other end of the load is connected to system ground. The voltage across the load constitutes the output of the amplifier circuit.

The operation of the circuit of fig. 6 is substantially the same as that described above in connection with fig. 1, with the only difference being that another voltage divider formed by resistors R5 and R6, which is not present in the circuit of fig. 1, is added to the circuit of fig. 6. In the present embodiment, input V_inIs applied to an amplifier 10, the same input V but of only half the amplitude_inThe/2 is applied to the amplifier 20. As with the circuit of fig. 5, these inputs may be from a source, such as a digital source with a digital-to-analog converter used to obtain the above configuration.

Fig. 7 shows an amplifier circuit according to a fourth embodiment of the present invention. The circuit includes two identical amplifiers: a main amplifier (X1)10 and a second amplifier (X2) 20. Both amplifiers have the gain G required by the whole system_VTwice as much. Since the amplifiers are identical, they will produce a similar error E during amplification. Ideally, the same operating conditions, such as the same supply voltage, the same input voltage, and the same load impedance, are applied to the amplifiers 10 and 20.

In the system of FIG. 7, the input signal V_inIs applied to a first point (point 1) and then to the positive input of the main amplifier 10. The input signal is also applied to a first end of a first resistor R1, the other of the first resistor R1The terminal is connected to a first terminal of a second resistor R2. The other end of the second resistor R2 is connected to system ground. The first and second resistors R1 and R2 form a voltage divider, the junction of which (point 5) is connected to the positive input of the second amplifier 20. The negative input of the second amplifier 20 is connected to system ground at point 2.

The output of the second amplifier 20 is connected at point 3 to a first end of a third resistor R3, the other end of the third resistor R3 being connected to a first end of a fourth resistor R4. A second end of the fourth resistor R4 is connected to system ground.

The junction of the third and fourth resistors R3 and R4, referred to as point 4, is connected to the negative input 9 of the main amplifier 10. The output of the main amplifier 10 is connected to a load R_loadThe load may be, for example, another amplifier such as a power amplifier, in which case the load R_loadIs a resistive element to ground or the load may be another element such as a loudspeaker. Load R_loadAnd the other end of the same is connected to system ground. Load R_loadThe voltage across it constitutes the output of the amplifier circuit. Another resistor R7 is connected across the output of the amplifier 10 and system ground to the load R_loadAnd (4) connecting in parallel.

The load on the amplifier 10 will depend on the load R connected to the amplifier system by the user_loadAnd therefore resistor R7 is included to reduce the variation in the total load applied to the system. For example, if the implementation is for a preamplifier, the load R_loadMay be another amplifier having a typical input impedance between 10K ohms and 47K ohms. If as shown in FIG. 7, with R_loadWith the addition of a resistor R7 having a typical value of 1K ohms in parallel, the load on the amplifier 10 is the resistors R7 and R_loadParallel connection (R7// R)_load) The effective resistance of (c). Thus, the range of load conditions will be narrowed accordingly, becoming:

r7// R if the input impedance of the load is 10K ohms_load1K//10K 909 ohms, and

if the input impedance of the load is 47K ohms, then R7// R_load1K//47K 979 ohms.

Meanwhile, the resistance value of the resistor R3+ R4 may be set between about 909 ohms and about 979 ohms so that the load conditions of the amplifier 10 and the amplifier 20 are close to each other.

Thus, the circuit of fig. 7 is identical to the circuit of fig. 1, except that another resistor R7 has been added thereto. The operation of the circuit of fig. 7 is substantially the same as described above in connection with fig. 1.

Fig. 8 shows an amplifier circuit according to a fifth embodiment of the present invention. The circuit includes two identical amplifiers: a main amplifier (X1)10 and a second amplifier (X2) 20. Both amplifiers have the gain G required by the whole system_VTwice as much. Since the amplifiers are identical, they will produce a similar error E during amplification. Ideally, the same operating conditions, such as the same supply voltage, the same input voltage, and the same load impedance, are applied to the amplifiers 10 and 20.

In the system of FIG. 8, the input signal V_inIs applied to a first point (point 1) and then to the positive input of the main amplifier 10. The input signal is also applied to a first end of a first resistor R1, the other end of the first resistor R1 being connected to a first end of a second resistor R2. The other end of the second resistor R2 is connected to system ground. The first and second resistors R1 and R2 form a voltage divider, the junction of which (point 5) is connected to the positive input of the second amplifier 20. The negative input of the second amplifier 20 is connected at point 2 to the junction of two further resistors R8 and R9. The other end of R9 not connected to R8 is connected to system ground. The end of resistor R8 not connected to resistor R9 is connected to the output of amplifier 20 to control the gain of amplifier 20 by applying feedback.

The output of the second amplifier 20 is connected at point 3 to a first end of a third resistor R3, the other end of the third resistor R3 being connected to a first end of a fourth resistor R4. A second end of the fourth resistor R4 is connected to system ground.

The junction of the third and fourth resistors R3 and R4, referred to as point 4, is connected to another resistor R11, the other end of which resistor R11 is connected to the negative input 9 of the main amplifier 10. Another resistor R10 is connected between the negative input of amplifier 10 and the output of amplifier 10 at point 6 to control the gain of amplifier 10 by applying feedback. Preferably, the values of the resistors R8, R9, R10 and R11 are selected so that the gains of the amplifiers 10 and 20 are substantially the same.

The output of the main amplifier 10 is connected to one end of a load, which may be, for example, another amplifier such as a power amplifier, in which case the load is a resistive element to ground, or another element such as a speaker. The other end of the load is connected to system ground. The voltage across the load constitutes the output of the amplifier circuit.

Thus, the circuit of fig. 8 is identical to the circuit of fig. 1, except that additional resistors R8 to R11 are added thereto. The operation of the circuit of figure 8 is substantially the same as that described above in connection with figure 1, with the only difference being that feedback is applied to both amplifiers 10 and 20 to control the gain of the amplifiers.

Thus, one or more embodiments of the present invention may provide an amplifier system in which the bandwidth is significantly wider than conventional amplifiers and with less phase shift and minimal distortion due to the elimination of distortion errors generated by individual amplifiers in the circuit.

The amplifiers 10 and 20 used in the simulation to obtain the above-described pattern have no feedback applied internally. However, embodiments of the invention may be applied to amplifiers with or without feedback.

Various modifications may be made to the embodiments of the present invention described above. For example, other components and method steps may be added to or substituted for those described above. Therefore, while the invention has been described above using specific embodiments, it will be apparent to those skilled in the art reading this disclosure that various changes may be made within the scope of the claims without departing from the spirit and scope of the invention.

Claims (28)

1. An amplifier system, comprising:

a first amplifier arranged to receive an input signal;

a second amplifier arranged to receive a portion of the input signal, the second amplifier having an output signal; and

a first voltage divider arranged to receive the output signal of the second amplifier and feed a portion of the output signal to the first amplifier;

wherein the first amplifier is arranged to subtract the portion of the output signal of the second amplifier from the input signal to produce a difference signal that is amplifiable by the first amplifier.

2. An amplifier system according to claim 1, further comprising a second voltage divider arranged to receive said input signal and feed said portion of said input signal to said second amplifier.

3. The amplifier system of claim 1, wherein the first and second amplifiers are identical.

4. The amplifier system of claim 2, wherein the second voltage divider comprises two equal resistive components.

5. The amplifier system of claim 4, wherein the resistive component is a high precision component.

6. An amplifier system according to claim 1, wherein said amplifier system has an overall gain and each of said first and second amplifiers has an associated gain, said gain associated with each of said first and second amplifiers being twice the overall gain of said amplifier system.

7. An amplifier system according to claim 6, wherein said first voltage divider comprises a first resistive component and a second resistive component, each of said first and second resistive components having an associated resistance, the ratio of said resistance associated with said first resistive component to said resistance associated with said second resistive component being such that the amplitude of a portion of the output signal of said second amplifier at the junction of said first and second resistive components fed to said first amplifier is equal to the amplitude of the output signal of said second amplifier divided by the gain of said second amplifier.

8. An amplifier system according to claim 7, wherein said first amplifier has an output, and wherein the sum of the associated resistances of said first and second resistive components of said first voltage divider is equal to a resistive load applied to said output of said first amplifier.

9. The amplifier system of claim 1, wherein the portion of the input signal received by the second amplifier is 50%.

10. An amplifier system according to claim 3, wherein said first and said second amplifiers have the same error generated therein, said error being cancelled by subtracting the error generated in said second amplifier from the error generated in said first amplifier.

11. An amplifier system according to claim 2, further comprising a third voltage divider arranged to receive said input signal and feed a portion of said input signal to said first amplifier.

12. An amplifier system according to claim 11, wherein said portion of said input signal received by said second amplifier is 50% of said signal portion received by said first amplifier.

13. An amplifier system according to claim 2, wherein the first amplifier has an output, the system further comprising a resistive element connected between the output of the first amplifier and system ground, the resistive element being arranged to reduce load variations of the first amplifier.

14. The amplifier system of claim 2, wherein each of the first and second amplifiers has a negative input and an output, the system further comprising a first resistive element connected between the negative input of the second amplifier and ground, and a second resistive element connected between the output of the second amplifier and the negative input of the second amplifier for setting the gain of the second amplifier by feedback.

15. An amplifier system according to claim 14, further comprising a third resistive element connected between the negative input of said first amplifier and the connection point of the resistors constituting said first voltage divider, and a fourth resistive element connected between the output of said first amplifier and the negative input of said first amplifier for setting the gain of said first amplifier by feedback.

16. A method of amplifying a signal, comprising:

applying an input signal to a first amplifier;

applying a portion of the input signal to a second amplifier, the second amplifier having an output signal;

applying the output signal of the second amplifier to a first voltage divider;

applying a portion of the output signal to the first amplifier; and

subtracting the portion of the output signal of the second amplifier from the input signal in the first amplifier to produce a difference signal that is amplifiable by the first amplifier.

17. The method of claim 16, further comprising applying the input signal to a second voltage divider, the portion of the input signal applied to the second amplifier being applied by the second voltage divider.

18. The method of claim 17, wherein the first and second amplifiers are identical and the second voltage divider comprises two equal resistive components, the step of applying a portion of the input signal to the second amplifier comprising applying 50% of the input signal to the second amplifier.

19. The method of claim 16 wherein the amplifier system has an overall gain and each of the first and second amplifiers has an associated gain, the method further comprising setting the first and second amplifiers such that the gain associated with each of the first and second amplifiers is twice the overall gain of the amplifier system.

20. The method of claim 16, wherein the first voltage divider comprises a first resistive component and a second resistive component, each of the first and second resistive components having an associated resistance, the method further comprising selecting the resistive components such that a ratio of the resistance associated with the first resistive component and the resistance associated with the second resistive component is such that an amplitude of a portion of the output signal of the second amplifier at a junction of the first and second resistive components that is fed to the first amplifier is equal to an amplitude of the output signal of the second amplifier divided by a gain of the second amplifier.

21. The method of claim 16, wherein the first amplifier has an output, the method further comprising: applying a resistive load to the output of the first amplifier such that the sum of the associated resistances of the first and second resistive components of the first voltage divider is equal to the applied load.

22. The method of claim 16, wherein the first and the second amplifiers have the same error generated therein, the method further comprising canceling the error by: subtracting the error generated in the second amplifier from the error generated in the first amplifier.

23. The method of claim 17, further comprising applying the input signal to a third voltage divider and applying a portion of the input signal to the first amplifier through the third voltage divider.

24. The method of claim 23, wherein the portion of the input signal received by the second amplifier is 50% of the signal applied to the first amplifier by the third voltage divider.

25. The method of claim 17, further comprising reducing load variations of the first amplifier using a resistive element connected between an output of the first amplifier and system ground.

26. The method of claim 17, wherein each of the first and second amplifiers has a negative input and an output, the method further comprising setting the gain of the second amplifier by feedback applied by connecting a first resistive element between the negative input of the second amplifier and ground and a second resistive element between the output of the second amplifier and the negative input of the second amplifier.

27. The method of claim 26, further comprising setting the gain of the first amplifier by feedback applied by connecting a third resistive element between the negative input of the first amplifier and the junction of the resistors forming the first voltage divider, and a fourth resistive element between the output of the first amplifier and the negative input of the first amplifier.

28. An audio amplifier system comprising the amplifier system of claim 1.