JPS6290010A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To reduce number of components and to decrease manufacturing cost by adopting the constitution that a bias voltage of a processing circuit of the 2nd preamplifier circuit element is applied directly from the bias circuit of the 1st preamplifier circuit element. CONSTITUTION:Pins No.3, 4 being signal output terminals of a reproducing amplifier 1 are connected directly to pins No.6, 7 being signal input terminals of a preamplifier 2. That is, the circuit is constituted that the bias voltage required for the processing circuit provided in the inside of the preamplifier 2 is obtained directly from a DC bias circuit of the reproducing amplifier 1, the bias voltage of the reproducing amplifier 1 and the bias voltage of the preamplifier 2 are made coincident. Then the level difference between the pins No.3, 4 of the reproducing amplifier 1 and pins No.6, 7 of the preamplifier 2 is lost and no insertion of a coupling capacitor between connection lines is required and number of components is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an amplifier circuit used in audio equipment such as a radio set 1 to a tape recorder.

[Technical blueprint of the invention 1 Conventionally, the sound of cassette tape recorders with radio etc. y31
The device is provided with an amplifier circuit for amplifying the audio signal reproduced from the magnetic head and the audio signal output from the tuner and outputting it from the speaker.

The amplification circuit of a typical acoustic resonator consists of a preamplifier circuit element (hereinafter referred to as a preamplifier) that performs the first stage amplification of the audio signal to be reproduced, and a main amplification circuit element (hereinafter referred to as a preamplifier) that performs the final stage amplification of the reproduced audio signal.
It has a two-stage configuration with a power amplifier (hereinafter referred to as a power amplifier).

FIG. 3 shows the configuration of a conventional amplifier circuit for audio equipment.

As can be seen from the figure, this circuit is an IC that amplifies the audio signal reproduced from the magnetic head of the tape recorder section in the first stage.
A reproducing amplifier 1 of the configuration, a preamplifier 2 of an IC@configuration that inputs the signal output from the reproducing amplifier 1, and outputs a signal obtained by amplifying this input signal or a signal input from another, and the preamplifier 2 of the IC It is comprised of a recording amplifier 3 having an IC configuration that amplifies the audio signal so as to supply it to the magnetic head of the tape recorder section.

Here, as for the connection of each amplifier, the lines from the magnetic head are connected to pins 1 and 2, which are the signal input terminals of reproduction amplifier 1, and the lines from the magnetic head are connected to pins 3 and 4, which are signal output terminals.
The number pins are coupling capacitors C1 and C2 respectively.
The 6th and 7th pins, which are signal input terminals of the preamplifier 2, are connected to the 6th and 7th pins.

And pins 8 and 9 are the signal output terminals of preamplifier 2.
Pin number is also the coupling capacitor C3 and C4.
It is connected to the 11th pin and the 12th pin which are the signal input terminals of the recording amplifier 3 via.

Note that pin 13 and 1 are the signal output terminals of recording amplifier 3.
The fourth pin is connected to the magnetic head.

By the way, the above-mentioned reproduction amplifier 1 is provided with a bias circuit for applying a DC bias to the magnetic head during recording, and the bias voltage from this bias circuit is supplied to the magnetic head from the No. 5 pin.

Also, the preamplifier 2 has a No. 10 pin that is the bias voltage input terminal of the processing circuit that receives δ internally.
This No. 10 pin is connected to ground via a capacitor C5.

Note that since the recording amplifier 3 is a common element with the reproduction amplifier 1, it also has a No. 15 pin connected to the bias circuit. Note that the 15th pin of the recording amplifier 3 is connected to the ground via a capacitor C6.

[Problems with the Aogai technology] However, in the conventional amplifier circuit as described above, the bias voltage of the preamplifier 2 is different from the bias voltage of the reproducing amplifier 1. A DC cut capacitor is inserted between the connection line between pin 3 and pin 4 and pin 6 and pin 7 of preamplifier 2, but this method increases the number of parts and increases the manufacturing cost. I was disappointed.

[Object of the Invention 1] The present invention has been made in order to solve these conventional problems, and its purpose is to provide an amplification circuit for a sound W device with a small number of parts and a low manufacturing cost.

[Summary of the Invention] That is, the present invention includes a first preamplifier circuit element provided inside a bias circuit that performs the function of amplifying a first signal and generates a DC bias voltage, and a second A processing circuit that amplifies a signal, receives a signal output from the first preamplifier circuit element, has a function of selectively outputting the input signal or the amplified signal, and supplies a bias voltage. and a second preamplifier circuit element disposed therein, wherein the bias voltage of the processing circuit of the second preamplifier circuit element is directly connected to the bias voltage of the processing circuit of the first preamplifier circuit element. The invention is characterized in that it is configured to be supplied.

[Embodiment 1 of the Invention Hereinafter, details of an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing the configuration of a circuit according to an embodiment of the present invention, and parts common to those in FIG. 3 are given the same reference numerals.

The circuit of this embodiment has the function of amplifying the audio signal input from the magnetic head in the first stage, and is equipped with an internal bias circuit that generates a DC bias voltage. The audio signal output from the tuner, microphone, etc. is input to the reproducing amplifier 1 of the configuration and is amplified in the first stage, while the audio signal amplified from the reproducing amplifier 1 is packed and the input audio signal or the amplified audio signal is Equipped with a function to selectively output audio signals that
The preamplifier 2 includes an IC-configured preamplifier 2 such as TA7797P (manufactured by Toshiba Corporation, trade name), which is provided with a processing circuit to supply a bias voltage.

The playback amplifier 1 has signal input terminals, pins 1 and 2.
The DC bias voltage from the internal bias circuit is connected to the magnetic head and preamplifier 2 via pin 5.
It is connected to pin 10, which is the bias voltage input terminal of the .

Further, the signal output terminals of the reproduction amplifier 1, pins 3 and 4, are directly connected to the signal input terminals of the preamplifier 2, which are the 6th pin and the 7th pin.

And pins 8 and 9 are the signal output terminals of preamplifier 2.
A selected audio signal is output from the number pin to a power amplifier (not shown).

The amplifier circuit of this embodiment is configured such that the bias voltage required by the processing circuit provided inside the preamplifier 2 can be obtained directly from the DC bias circuit of the reproducing amplifier 1. The bias voltage of 1 and the bias voltage of preamplifier 2 match, and the 3rd and 4th pins of playback amplifier 1 and the 6th and 7th pins of preamplifier 2 match.
There is no level difference between the number pin and the number pin, there is no need to insert a coupling capacitor between the connection lines, and the number of parts can be reduced.

FIG. 2 is a circuit diagram showing the configuration of a circuit according to another embodiment of the present invention.

This circuit is composed of a reproduction amplifier 1 and a preamplifier 2, which are common to the circuit shown in Fig. A resistor R1 is connected to the internal bias circuit or connected to the connection line, and a decoupling capacitor C7 is connected between the No. 10 pin and the ground.

With such a configuration, even if, for example, the amplitude of the audio signal output from the reproduction amplifier 1 is large and signal leakage occurs at the bias terminal of the reproduction amplifier 1, the influence of signal leakage can be avoided.

[Effects of the Invention] As explained above, the amplifier circuit of the present invention has the function of first-stage amplification of the first signal, and also includes a bias circuit that generates a DC bias voltage or a first preamplifier provided inside. a circuit element that amplifies the second signal while amplifying the first signal;
It has a function of inputting the signal output from the preamplifier circuit element and selectively outputting the input signal or the amplified signal, and has a 52-digit processing circuit internally provided with a bias voltage. two preamplifier circuit elements, configured such that the bias voltage of the processing circuit of the second preamplifier circuit element is directly supplied from the bias circuit of the first preamplifier circuit element. Therefore, there is no need to insert a coupling capacitor in the input/output line between each element, and the number of parts and manufacturing cost can be reduced.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a circuit diagram showing the configuration of a circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of a circuit according to another embodiment of the present invention, and FIG. FIG. 2 is a circuit diagram showing the configuration of an amplifier circuit of the audio device. 1......Playback amplifier 2...
・・・・・・Preamplifier 3・・・・・・・・・Recording amplifier C1-C4・・・Capacitor

Claims (1)

[Claims] (1) A first preamplifier circuit element that has a function of amplifying a first signal and is provided with a bias circuit that generates a DC bias voltage; a second preamplifier circuit element having a function of inputting a signal output from the first preamplifier circuit element and selectively outputting the input signal or the amplified signal, and having a processing circuit provided therein to supply a bias voltage; a preamplifier circuit element, and configured such that a bias voltage of the processing circuit of the second preamplifier circuit element is supplied directly from the bias circuit of the first preamplifier circuit element. An amplifier circuit characterized by: