JPH03182108A - Regenerative amplifier - Google Patents

Abstract

PURPOSE:To obtain a stable frequency characteristic by feeding the output of a feedback amplifier back to the input of a main amplifier, grounding the input of the main amplifier by a capacitor to suppress resonance peak with an induced magnetic head at the input. CONSTITUTION:The signal of a magnetic head 1 is amplified by a main amplifier 3 and outputted and through a feedback amplifier 4 which amplifies a low frequency component with a high gain and a high frequency component with a low gain, a frequency characteristic (a) shown in a figure is obtained. For the output, the feedback amount of the high frequency component to the input of the main amplifier 3 is controlled by a low-pass filter, which is composed of a resistor 6 and a capacitor 9 grounding the base of an input transistor in the main amplifier 3, and closed to a track in the figure and the resonance peak with the induced magnetic head at the input is suppressed. Thus, the stable frequency characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a reproduction amplification device for, for example, a video tape recorder (hereinafter referred to as VTR).

BACKGROUND OF THE INVENTION FIG. 3 shows a block configuration of a conventional VTR regenerative amplifier.

In FIG. 3, 1 is a magnetic head, 2 is a capacitor, 3 is a main amplifier, 4 is a feedback amplifier, 5 is a first resistor, 6 is a capacitor, 7 is a second resistor, and 8 is a third resistor.

Next, the operation of the conventional example will be explained. In Figure 3,
The signal from the magnetic head 1 is amplified by the main amplifier 3 and outputted.The signal is then passed through the feedback amplifier 4, which amplifies the low frequency component with a high gain and the high frequency component with a low gain, and the output is further transmitted through a resistor 5.7 and a capacitor 6. The high-frequency components are attenuated to a constant level while the low-frequency components remain unchanged to create a frequency characteristic similar to the locus shown in Figure 2, which is then fed back to the base of the input transistor of the main amplifier through the resistor 8, resulting in a resonance peak with the magnetic head 1 at the input. This results in stable frequency characteristics.

Problems to be Solved by the Invention However, the conventional configuration described above requires a resistor of 5°7.8 and a capacitor 6, which requires a large number of parts, and the frequency characteristics of the regenerative amplifier are unstable unless the capacitor 6 has a capacity of about 1 μ. When making a regenerative amplifier using a semiconductor integrated circuit, the capacity is 6.
It is difficult to incorporate the regenerative amplifier, and the conventional regenerative amplifier semiconductor integrated circuit has a problem in that a pin for connecting the capacitor 6 and the resistor 7 is required.

The present invention solves the above conventional problems, eliminates the capacitor 5 and resistor 6, stabilizes the frequency characteristics of the regenerative amplifier, reduces the number of parts, and reduces the number of pins and parts when fabricating a semiconductor integrated circuit. This makes it possible to reduce

Means for Solving the Problems In order to achieve the above objects, the present invention provides a regenerative amplifier in which the capacitor 6 and the resistors 7 and 8 are removed, and the base of the input transistor of the main amplifier is grounded through the capacitor 9.

In a conventional regenerative amplifier, the high frequency component of the output of the feedback amplifier 4, which amplifies the low frequency component with a high gain and the high frequency component with a low gain, is attenuated to a constant value by the capacitor 6 and the resistor 5.7, and the high frequency component is amplified by the ratio of the resistors 5 and 7. Stable frequency characteristics were achieved by adjusting the amount of feedback to the input of the main amplifier.

The locus in FIG. 2 is the frequency characteristic of the feedback system composed of the feedback amplifier 4, resistors 5, 7, and capacitor 6.

f3 and f4 are the frequency characteristics of the feedback amplifier 4, fl and f
2 is a frequency characteristic due to resistance 5.7 and capacitance 6.

When the capacitor 6 is made smaller, f1 and f2 become larger, and when f2 becomes larger than f3, the feedback amplifier 4 and the resistor 5,
Since positive feedback occurs in one part of the feedback system composed of the capacitor 7 and the capacitor 6, the frequency characteristics become unstable, making it difficult to incorporate the capacitor 6 and the resistor 7 in a semiconductor integrated circuit.

In the present invention, in order to solve this problem, the capacitor 6 and the resistor 7 are
, 8 are removed, and the high frequency component of the output of the feedback amplifier 4 having the frequency characteristic represented by the locus shown in FIG.
By adjusting the amount of feedback to the input of the main amplifier 3 using a low-pass filter composed of a resistor 5 and a resistor 5, stable frequency characteristics were achieved.

Operation The present invention has the above-described configuration, so that the output of the feedback amplifier 4 having the frequency characteristic represented by the locus shown in FIG. The low-pass filter consisting of capacitance 9 adjusts the amount of feedback of high frequency components to the input of the main amplifier to suppress the resonance peak with the inductive magnetic head at the input and obtain stable frequency characteristics. The resistors 7 and 8 and the capacitor 6 can be reduced instead of adding a 1. This reduces the number of parts of the regenerative amplifier and when the regenerative amplifier is integrated into a semiconductor integrated circuit, the pin connecting the capacitor 6 and the resistor 7 is unnecessary, and the pin The number can be reduced.

Embodiment FIG. 1 shows a block configuration of a regenerative amplifier according to an embodiment of the present invention.

In Fig. 1, 1 is a magnetic head, 2 is a capacitor, and 3 is a magnetic head.
is a main amplifier, 4 is a feedback amplifier, 6 is a resistor, and 9 is a capacitor.

Next, the operation of the above embodiment will be explained. In the above embodiment, the signal from the magnetic head 1 is amplified and outputted by the main amplifier circuit 3, and is also passed through the feedback amplifier 4, which amplifies the low frequency component with a high gain and the high frequency component with a low gain, as shown in FIG.
The output is connected to a resistor 5 and a capacitor 9 that connects the base of the input transistor of the main amplifier 3 to ground.
The amount of feedback of high frequency components to the input of the main amplifier is adjusted by a low-pass filter consisting of a has been realized.

Effects of the Invention As is clear from the above embodiments, the present invention has the effect of reducing the number of components of a regenerative amplifier and making it possible to create a regenerative amplifier with a reduced number of bins suitable for semiconductor integrated circuits.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a regenerative amplifier according to an embodiment of the present invention.
FIG. 2 is a diagram showing the frequency characteristics of the feedback amplifier of the present invention and a conventional regenerative amplifier, and FIG. 3 is a block diagram of the conventional regenerative amplifier.

Claims (1)

[Claims] The output of the main amplifier is input to a feedback amplifier that amplifies low frequency components with high gain and high frequency components with low gain,
Reproduction characterized in that the output of the feedback amplifier is fed back to the input of the main amplifier through a first resistor, and the input of the main amplifier is grounded by a capacitor to suppress resonance peaks with the inductive magnetic head at the input. amplifier.