JPH06291563A - Audio amplifier - Google Patents

Abstract

PURPOSE:To obtain an audio amplifier in which high frequency noise components intruding into a feedback circuit can be reduced, and a satisfactory sound quality can be obtained by allowing the high frequency noise components intruding from an output terminal to pass through an emitter resistor and absorbing them by the emitter of a transistor with a low output impedance. CONSTITUTION:The connecting point of an emitter resistor 2a of an NPN type transistor 1a and an emitter resistor 2b of a PNP type transistor 1b is connected to an output terminal 6, and the emitter of the NPN type transistor 1b and the emitter of the PNP type transistor 1b are connected to a capacitor 4. Also, the emitter of the NPN type transistor 1a and the emitter of the PNP type transistor 1b are respectively connected to a resistor 3a and a resistor 3b, and the connecting point of the resistor 3a and the resistor 3b is connected to a feedback circuit 11. The unbalanced operation of the high frequency area of the NPN type transistor 1a and the PNP type transistor 1b can be prevented by the capacitor 4 to which the emitter of the NPN type transistor 1a and the emitter of the PNP type transistor 1b are connected.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to audio amplifiers.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing an audio amplifier having a conventional push-pull output stage. In the audio amplifier, a device connected to the connection cable 7 causes a high-frequency noise component to conversely enter the feedback circuit 11 through the output terminal 6. In the circuit of FIG. 2, the transistor 1
Due to the emitter resistance 2a and the emitter resistance 2b for stabilizing the bias currents of a and 1b, the high frequency noise component that has entered from the output terminal 6 cannot be sufficiently absorbed by the emitters of the transistors 1a and 1b, so that the high frequency noise is not absorbed. The component enters the feedback circuit 11 through the feedback resistor 11a and is input to the inverting input terminal 10a of the voltage amplification stage.

When a high frequency noise component penetrates into the feedback circuit of the audio amplifier, it is a cause of generating TIM distortion, which is particularly harmful to the sense of hearing. Distortion caused by high-frequency noise components such as TIM distortion is very harmful to the sense of hearing,
It has been difficult for the conventional technology to provide an audio amplifier with good sound quality.

[0004]

The problem to be solved by the present invention is to reduce the intrusion of the high frequency noise component that has entered from the output terminal 6 of the audio amplifier into the feedback circuit 11, and the high frequency noise component causes the audio amplifier to operate. Another object of the present invention is to provide an audio amplifier which prevents distortion and has a good sound quality in terms of hearing.

[0005]

In order to achieve the above object, the connection point between the emitter resistor (2a) of the NPN transistor (1a) and the emitter resistor (2b) of the PNP transistor (1b) is connected to the output terminal ( 6), connect to NPN
Type transistor (1a) and PNP type transistor (1
Connect the emitter of b) with a capacitor (4), and separate N
The emitters of the PN type transistor (1a) and the PNP type transistor (1b) are connected by the resistor (3a) and the resistor (3b), and the connection point of the resistor (3a) and the resistor (3b) is connected to the feedback circuit (11). .

[0006]

In the audio amplifier configured as described above, the high frequency noise component that has entered from the output terminal (6) passes through the emitter resistor (2a) and the emitter resistor (2b), and the transistors (1a) and (1) having a low output impedance.
Since it is absorbed by the emitter of b), the high frequency noise component entering the feedback circuit (11) via the resistors 3a and 3b is significantly reduced.

The capacitor (4) in which the emitter of the NPN transistor (1a) and the emitter of the PNP transistor (1b) are connected to each other is the NPN transistor (1a).
And to prevent unbalanced operation of the PNP transistor (1b) in the high frequency region.

[0008]

1 is a circuit diagram showing an embodiment of the present invention, in which 1 is a transistor, 2 is an emitter resistor, 3 is a resistor according to the present invention, 4 is a capacitor according to the present invention, 5 is an output resistor, 6 is an output terminal, 7 is a connection cable, 8 is a power supply, 9
Is a bias circuit, 10 is a voltage amplification stage, 10a is an inverting input terminal, 10b is a non-inverting input terminal, 11 is a feedback circuit, 12
Is an input terminal.

FIG. 1 shows an example in which the output resistor 5 is provided between the output terminal 6 and the connection point between the emitter resistors 2a and 2b.

[0010]

With such a structure, most of the high-frequency noise components that have entered from the output terminal 6 of the audio amplifier are the transistor 1 having a low output impedance.
It is absorbed by the emitter of a and the emitter of the transistor 1b.

Therefore, the high frequency noise component that enters the feedback circuit 11 is reduced, and the distortion caused by the high frequency noise component such as TIM distortion is reduced. Therefore, an audio amplifier with good sound quality can be obtained.

The capacitor 4 is composed of the NPN type transistor 1a and the PNP type transistor 1 in the high frequency range.
This is for averaging the characteristic differences such as the output impedance of b to prevent unbalanced operation with respect to high frequency noise components.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an audio amplifier according to the present invention.

FIG. 2 is a circuit diagram of a conventional audio amplifier.

[Explanation of symbols]

1 Transistor 1a NPN type transistor 1b PNP type transistor 2 Emitter resistance 2a NPN type transistor emitter resistance 2b PNP type transistor emitter resistance 3 Resistor according to the present invention connected in parallel with emitter resistance 3a NPN type transistor emitter connected,
Connected to the emitter of a resistor 3b PNP transistor according to the invention,
Resistance 4 according to the present invention Capacitor 5 according to the present invention 5 Output resistance 6 Output terminal 7 Connection cable 7a Connection cable core wire 8 Power supply 8a Positive power supply 8b Negative power supply 9 Bias circuit 10 Voltage amplification stage 10a Inversion input terminal 10b Non-inverting input terminal 11 Feedback circuit 11a Feedback resistor 11b Feedback resistor 12 Input terminal

Claims (1)

[Claims] 1. An audio amplifier having a push-pull output stage, comprising an NPN transistor (1a) and a PNP transistor (1b), comprising:
Type transistor (1a) emitter resistance (2a) and PN
The connection point of the emitter resistance (2b) of the P-type transistor (1b) is connected to the output terminal (6), the emitters of the NPN-type transistor (1a) and the PNP-type transistor (1b) are connected by the capacitor (4), and separately. The emitters of the NPN-type transistor (1a) and the PNP-type transistor (1b) are connected by the resistor (3a) and the resistor (3b), and the connection point of the resistor (3a) and the resistor (3b) is connected to the feedback circuit (11). An audio amplifier characterized by being connected.