JPS6133704Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier device used as, for example, an audio power amplifier.

Generally, when a power amplification stage composed of power transistors, power FETs, etc. is operated in class B or class AB, large distortion occurs. For this reason, recent audio amplifiers apply a large amount of negative feedback in order to reduce distortion. However, in order to stabilize the negative feedback, a phase compensation circuit is used to reduce the amount of feedback in the high frequency range. For this reason, distortion in the high frequency range of the amplifier increases as the amount of feedback decreases.

However, a feed forward method is known as a technique for canceling such distortion. FIG. 1 is a block diagram showing an example of a conventional feed-forward type amplifier. In the figure, 1 is an input terminal to which a signal to be amplified is given, 2 is an impedance element 3 that amplifies the signal given from input terminal 1, and
This is a large power amplifier with relatively poor linearity that supplies power to the load 4 via the power amplifier. And 5 is an impedance element 6 which amplifies the difference voltage between the input and output of the high power amplifier 5.
This is a small power amplifier with relatively good linearity that supplies the power to the load 4 via the high power amplifier 2 and cancels out the distortion components generated in the high power amplifier 2.

However, in such a device, the voltage at the signal application end of the load 4 fluctuates with the output, and the apparent
The output voltage of the small power amplifier 5 increases. For this reason, the output current of the small power amplifier 5 becomes large and large distortion occurs, making it impractical, or a large power amplifier with good linearity is required instead, which is impractical.

The present invention was developed in view of the above circumstances, and uses a small power amplifier to obtain only a correction signal for distortion components.
It is an object of the present invention to provide an amplifier device that can reliably cancel out distortion generated in a high-power amplifier.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the block diagram shown in FIG. 2, in which the same parts as in FIG. 1 are given the same reference numerals. That is, high power amplifier 2
An impedance element 7 is inserted on the reference potential side of the load 4 which is supplied with the output. Then, the output current of the small power amplifier 5 is supplied via the impedance element 6 to the connection point between the load 4 and the impedance element 7. In this case, the impedance elements 6 and 7 adjust the level and phase of the outputs of the large power amplifier 2 and the small power amplifier 5, and cancel the distortion components generated in the large power amplifier 2 with the correction current output from the small power amplifier 5. That's what I do. Note that as the impedance elements 6 and 7, a coil, a capacitor, or a series circuit of a resistor and a coil or capacitor, etc. are used as appropriate.

It should be noted that the present invention is not limited to the above-mentioned embodiment; for example, a preamplifier 8 may be provided between the input terminal 1 and the high power amplifier 2 as shown in the block diagram of FIG. Then, the output of the high power amplifier 2 is negatively fed back to the inverting input of the preamplifier 8 via the feedback circuit 9. In this case, since the design is such that the amount of feedback is reduced in the high frequency range so that negative feedback can be stably applied, the distortion component included in the output of the large power amplifier 2 increases toward the high frequency range.
Therefore, it is necessary that the correction current for the distortion component in the small power amplifier 5 also increases toward higher frequencies. Therefore, in this case, a coil or a series circuit of a coil and a resistor is used as the impedance element 7 inserted on the reference potential side of the load 4, and a capacitor or a series or series-parallel circuit of a capacitor and a resistor is used as the impedance element 6. Bye.

In this way, since only the distortion component correction current is obtained from the small power amplifier 5, it is possible to use an amplifier with relatively small output and good linearity, and it is possible to obtain good characteristics over a wide frequency band.

As detailed above, in the present invention, an impedance element is inserted into the reference potential side of the load to which the output of the large power amplifier is applied, and the voltage difference between the input and output of this large current amplifier is amplified and transmitted through the impedance element. This signal is supplied to the reference potential side of the load to cancel out the distortion caused by the high power amplifier. Therefore, it is possible to provide an amplifier that can cancel out the distortion caused by a high power amplifier and obtain good characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a block diagram showing one embodiment of the present invention, and FIG. 3 is a block diagram showing another embodiment of the present invention. 1...Input terminal, 2...High power amplifier, 4...
Load, 5... small power amplifier, 6... impedance element, 7... impedance element.

Claims (1)

[Scope of utility model registration request] A first amplifier with relatively poor linearity amplifies an externally applied signal and supplies it to one end of the load on the non-reference potential side, and a first amplifier inserted between the other end of the load and the reference potential. The voltage difference between the input and output of the impedance element and the first amplifier is amplified and supplied to the other end of the load via a second impedance element to cancel the distortion generated in the first amplifier. and a second amplifier with relatively good linearity.