JPH0352026Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for correcting an alternating current output signal from a main amplifier, such as an electronic device, responsive to a variable input signal.

An alternating current output signal from an electronic device in response to an alternating current input signal may be picked up by the load associated with the output signal, the design constraints of the electronic device, and the equipment that conveys the output signal or otherwise It is affected by external deterioration factors such as noise or parasitic capacitance. Each of these factors degrades the amplitude and phase accuracy of the desired output signal from the input signal.

Accurately corresponding output signals to input signals is often important for electronic device applications. This is why, for example, the distortion of the output signal relative to the input signal is a well-known measure of amplifier quality.

One common application for amplifiers in which the accuracy of the output signal relative to the input signal is important is in high frequency reproduction devices. These common devices amplify recorded or broadcast music (and audio) signals to drive speakers. The amplifier must accurately amplify the input signal so that the recorded sound can be accurately reproduced by the speaker.

However, from both a cost perspective and a technical perspective such as gain, amplifier design requires compromises between amplifier cost or amplifier gain and signal reproduction accuracy. It is often necessary to teach. Similarly, due to cost or space design considerations, it is often difficult to completely shield the output side of an amplifier from noise and parasitic capacitances that degrade the output signal. However, since most of these factors occur within the amplifier, they can be controlled by the manufacturer within design constraints.

Many high frequency amplifier devices are commercially available separately from the speaker loads that are driven by the amplifier. Since all speakers do not exhibit the same characteristics, it is impossible to measure in advance the exact characteristics of the load to be coupled to the amplifier device. Furthermore, the load characteristics of the speakers are not uniform (as expected when designing a high-frequency amplifier). For example, many speakers have a resonant frequency within the range of audio frequencies they reproduce that significantly affects the electrical characteristics of the speaker load. Furthermore, many speakers have circuitry in which the frequency response characteristics cross over between the individual speaker arrays within the speaker, and these circuitries also respond to the frequency of the output signal to adjust the electrical characteristics of the speaker load. change.

It is an object of the present invention to provide a circuit for correcting an alternating current output signal from a main amplifier in response to a variable input signal from an electronic device such as an amplifier, the circuit comprising: a first input directly receiving the alternating current component of the input signal; a first amplifier having a terminal: a second amplifier having an output terminal connected in alternating current to the input terminal of the main amplifier; one end connected to the first input terminal of the first amplifier;
a variable input resistor whose sliding end is connected to the input terminal of the second amplifier; connection-disconnection means for connecting or disconnecting the output terminal of the first amplifier to the output terminal of the second amplifier; the sliding end is connected to the output terminal of the main amplifier,
variable resistance feedback means, one end of which is connected to a second input terminal of the first amplifier;
It is characterized in that an alternating current component of the difference between the signals supplied to the input terminal is supplied to the connection/disconnection means as a negative feedback signal.

It is of course important that the signals from the first and second amplifiers are accurate signals. However, since these amplifiers only act as correction circuits, they do not need to be subject to design constraints such as gain. Furthermore, since the electrical characteristics of the load driven by these amplifiers, that is, the electronic device, are known, the designer can fully consider the load characteristics of this electronic device. Due to the impedance design, changes in the signal to the electronic device are largely unaffected by the load characteristics of the device. Therefore, it is better to design inexpensive, high-precision first and second amplifiers for the correction circuit than to design high-precision electronic devices such as high-gain amplifiers for an unknown variable speaker load. It's easy.

Proper operation of the correction circuit accommodates load non-uniformities and non-uniformities in the operation of the electronic device. As already mentioned, in an example in which an amplifier and a speaker are combined, the load characteristics of many speakers are non-uniform. Also, the response of many amplifiers is non-uniform over the range of input signal frequencies and the gain at which the amplifier operates. Therefore, in order to operate the correction circuit, first the frequency and amplitude of the input signal and the amplifier (electronic device) are determined by the second amplifier (this second amplifier) of the correction circuit.
The amplifier does not receive a feedback signal from the electronic device. )
Determine the gain that most accurately responds only to the signal from. In this case, the amplitude of the feedback signal to the first amplifier of the correction circuit is adjusted until the alternating current signal from this first amplifier becomes zero. The output signals from the first and second amplifiers in the correction circuit are then combined for input to the electronic device.

The operation of the correction circuit after presetting as described above is as follows. As long as the input signal and the electronics are in the most accurate conditions as set out above, no alternating current signal will be produced by the first amplifier of the correction circuit. However, since the input signal is also supplied to the other (second) amplifier of the correction circuit, and this second amplifier does not receive feedback of the output signal from the electronic device, the second amplifier generates an output signal to the electronic device. supply a signal to

However, if a large distortion occurs between the input signal and the output signal, both amplifiers of the correction circuit will generate a signal, and the signal from the first amplifier in this case will be equal to the difference between the input signal and the output signal. Since it is a function, the signal from the first amplifier changes inversely to the distortion of the output signal. Combining the signals from both amplifiers of the correction circuit therefore provides the electronic device with a signal that compensates for the distortion in the output signal.

For example, if the output signal is too small, the signal from the first amplifier of the correction circuit that receives feedback of the output signal will be reduced and the combined signal to the electronic device will be increased, thereby increasing the output signal. Output signals which are too large and which are phase shifted from the input signal are corrected accordingly by the correction circuit. The operation of the correction circuit is therefore independent of the sources of inaccuracy (distortion) in the output signal; the correction circuit is independent of sources of inaccuracy (distortion) in the output signal, for example due to noise or parasitic factors at the output of the electronic device or to load fluctuations in the electronic device. Therefore, distortions occurring internally in the electronic device can be corrected.

The invention will be explained with reference to the drawings.

FIG. 1 shows an example of an AC output signal correction circuit according to the present invention, and this circuit includes a first amplifier (AMP.-1) and a second amplifier (AMP.-2).
It has 12. An electronic device 14 that supplies an output signal to a terminal 16 to be corrected by this correction circuit.
is also shown as a main amplifier (AMP.-3) like amplifiers 10 and 12 above. The electronic device 14 may be, for example, a conventional type of amplifier used in commercially available high-fidelity reproduction equipment. In this case, the output load (not shown) connected to the output signal arriving at terminal 16 may be a speaker. However, electronic device 1
4 can also be any other type of electronic device that generates an AC output signal in response to an AC input signal.

The output signal at terminal 16 is passed through a path comprising a variable resistor 18 to a first amplifier 10 in the correction circuit.
feed back to the input terminal of In this case the first amplifier 1
0 provides an output signal at terminal 20 that is a function of the difference between the input signal provided at input terminal 22 and the feedback (output) signal.

The input signal at the terminal 22 is also supplied to the second amplifier 12 of the correction circuit via a path comprising a variable resistor 24 . The signal from this second amplifier 12 is passed through the path 2.
6 to the electronic device 14 as a main amplifier. The signal from the first amplifier 10 is combined with the signal from the second amplifier 12 via path 28, and the signal from the first amplifier 10 is part of the signal input to the electronic device 14, as will be described in more detail below in circuit operation. Also supplied as The passageway 28 is provided with connection-disconnection means for keeping this passageway open during an initialization phase of the correction means for presetting the correction circuit for a particular electronic device 14, and for closing the passageway 26 during operation of the correction circuit. It is shown with a broken line to show that.

Figure 2 shows the first and second amplifiers 1 for the correction circuit.
2 is a circuit diagram showing in more detail the preferred embodiment of FIG. 1 with 0,12; FIG. As shown in FIG. 2, each of the first and second amplifiers is a single transistor amplifier, and these transistors 30 and 32 are N.
It can be in the form of product number 2AC945, which is commercially available from EC. The base of each transistor 30, 32 is connected to receive the input signal from terminal 22, and during operation of the correction circuit, paths 26 and 28 are connected to receive the input signal from the collector of both transistors 30, 32. is supplied to the electronic device 14 as a composite signal.

The resistance value range of resistor 18 may be about 10 times the output impedance of electronic device 14, or about 100-300 ohms for many commercially available amplifiers suitable as electronic device 14. resistance 2
Range 4 needs to be a relatively high value range, for example about 500KΩ. The values of other resistors, capacitors, and bias potentials shown in FIG. 2 can be appropriately set depending on the circuit design.

In order to ensure that the correction circuit comprising the first amplifier 10 and the second amplifier 12 does not itself induce any extra inaccuracies (distortions) in the output signal at terminal 16, the output signal is most similar to the input signal at terminal 22. It is advantageous to preset the correction circuit in such a way that it does not have any influence on the output signal during accurate correspondence. To this end, the correction circuit is preset by first determining, for example, the frequency of the input signal and the gain of the main amplifier 14 and the respective state of the output load for which the output signal at terminal 16 most accurately corresponds to the input signal. The most accurate correspondence of the output signal appearing at output terminal 16 to the input signal is often achieved with an input signal of a certain frequency and at the full gain of the amplifier. However, the most accurate conditions can be achieved using a variety of known devices and techniques, such as an oscilloscope.

In this case, first, a signal that produces a minimum distortion in the output signal at terminal 16 is supplied to terminal 22;
The resistor 24 is then adjusted so that the amplitude of the signal input from the amplifier 12 to the electronic device 14 via the path 26 is a suitable value, providing an output signal at the terminal 16 with minimum distortion. During such operation, path 28 is open and electronic device 14 receives only the signal from amplifier 12 via path 26.

The feedback signal to amplifier 10 is then adjusted by adjusting resistor 18 so that the AC signal at terminal 20, which is currently open, is zero. Therefore, if the output signal at output terminal 16 is substantially undistorted relative to the input signal at terminal 22, the correction circuit is preset so that this has no adverse effect on the output signal. This prevents the correction circuit from inducing extra distortion in the output signal.

The passageway 28 is then closed to the passageway 26 so that the signal from the amplifier 10 is provided to the passageway 26 to the input terminal to the electronic device 14. The input signal at terminal 22 no longer needs to be a signal that produces minimal distortion in the output signal. The correction circuit is thus preset so that the output signal remains unchanged with minimal distortion, but as mentioned above, the correction circuit is also arranged to correct large distortions of the output signal.

If the frequency and amplitude of the input signal at input terminal 22 are such as to provide minimal distortion to the output signal at terminal 16, amplifier 10
The AC output signal from remains zero. but,
The input signal is amplified by amplifier 12 via resistor 24 and provided to electronic device 14 via path 26, producing an alternating current output signal at output terminal 16 that corresponds very precisely to the input signal. However, terminal 2
When the input signal at 2 changes, both amplifiers 1 and 12 generate signals that are combined as inputs to electronic device 14 to generate an output signal at terminal 16.

As mentioned above, the electronic device 14 is like a high-fidelity regenerative amplifier (amplifier), and such an amplifier exhibits linear characteristics. Second
It is assumed that the amplifiers indicated by numerals 10 and 12 in the figure also exhibit linear characteristics. Therefore, as the amplitude of the input signal at terminal 22 increases, a signal is generated in path 26 that is amplified by the gain of amplifier 12;
Further, an output signal amplified by the gain of the amplifier 14 is generated at the terminal 16. These amplifiers are 1
If it exhibits the above absolute gain, the terminal 16
The amplitude of the output signal of increases with respect to the amplitude of the input signal. The AC output signal from amplifier 10 remains zero even though the output signal increases proportionally to the increase in input signal due to the gains of amplifiers 12 and 14. However, the output signal at terminal 16 is
If the output signal becomes too large relative to the input signal due to design constraints related to the input signal, changes in the output load (not shown), or changes in the noise picked up by the device carrying the output signal, the Amplifier 1 without invalidating the input signal of
Generates a decreasing AC output signal from zero. This reduced signal from amplifier 10 is combined with the output signal from amplifier 12 in path 26 to reduce the signal input to amplifier 14, so that the output signal at terminal 16 is reduced in proportion to the distortion. On the other hand, if the distortion of the AC output signal causes the AC output signal to decrease relative to the AC input signal, then resistor 18
The feedback output signal from to amplifier 10 decreases and the signal from amplifier 10 increases, which causes amplifier 14 to
As the input signal to increases, the output signal increases.

Therefore, as described above, the correction circuit corrects the amplitude value of the output signal with respect to the input signal, such that the amplitude level reaches the level of the minimum amplitude distortion of the output signal while the correction circuit is preset as described above. Make it. A similar operation occurs when the output signals have different phases. If the output signal lags the input signal in phase, the input signal causes the amplifier 10 to generate the signal earlier than the feedback signal;
Advancing the phase of the signal in path 26 to amplifier 14 advances the phase of the output signal at terminal 16. On the other hand, if the output signal leads the input signal in phase, then the output signal from amplifier 10 delays the input signal and adjusts the output signal accordingly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an AC output signal correction circuit according to the present invention, and FIG. 2 is a detailed circuit diagram thereof. 10...first amplifier, 12...second amplifier, 1
4...Electronic device (main amplifier), 16...Output terminal,
18...Variable resistor, 22...Input terminal, 24...
Variable resistor, 28...Connection-disconnection means, 30,3
2...transistor.

Claims (1)

[Claims for Utility Model Registration] A circuit for correcting an alternating current output signal from a main amplifier responsive to a variable input signal, the circuit having: a first input terminal for directly receiving an alternating current component of the input signal; a first amplifier having: a second amplifier having an output terminal connected to the input terminal of the main amplifier; and a second amplifier having one end connected to the first input terminal of the first amplifier;
a variable input resistor whose sliding end is connected to the input terminal of the second amplifier; connection-disconnection means for connecting or disconnecting the output terminal of the first amplifier to the output terminal of the second amplifier; the sliding end is connected to the output terminal of the main amplifier,
variable resistance feedback means, one end of which is connected to a second input terminal of the first amplifier;
An alternating current output signal correction circuit characterized in that an alternating current component of the difference between the signals supplied to the input terminal is supplied to the connection/disconnection means as a negative feedback signal.