JPS5840646Y2 - amplifier circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an amplifier circuit, and is particularly suitable for use in an audio amplifier circuit.

In a conventional amplifier circuit, one stage of a driver that drives a final stage having an input quadrature is constituted by a class A single amplifier circuit.

In this case, since it is a class A amplification, the current consumption is large, and since direct current flows through the input cadence, the magnetic core of the input cadence is magnetized by the direct current, resulting in poor frequency characteristics.

The present invention has been devised in view of the above-mentioned drawbacks, and includes a final stage having an input voltage lance, and a driver stage for driving the final stage.
It is configured with an EPP circuit.

With this configuration, current consumption can be reduced, and since no direct current flows through the input transformer, frequency characteristics can be improved.

The present invention will be explained below with reference to examples and FIGS. 1 and 2.

As shown in FIG. 1, a radio receiver 1 includes a tuner section 2 and a speaker section 3. As shown in FIG.

Further, the tuner section 2 is composed of a tuner 4, a driver stage 13 of an amplifier, and a power supply 6, and the speaker section 3 is composed of a final stage 14 of an amplifier and a speaker 8.

First, the case where the tuner section 2 is used separately from the speaker section 3 will be explained with reference to FIG.

In this case, connect earphone plug 4 to earphone jack 12.
1 is inserted and connected, and the earphones 11 are used for listening.

Although the earphone jack 12 is depicted in FIG. 1 as being provided on the coupling surface between the tuner section 2 and the speaker section 3, the earphone jack 12 may be provided on a surface other than the coupling surface. It's fine.

Earphone plug 41 connects earphone 11 and lead wire 42a
, 42b.

When the earphone plug 41 is inserted into the earphone jack 12, the terminal 12a of the earphone jack 12 connects to the lead wire 42.
The terminal 12 a is connected to the input terminal of the tuner 4 via the capacitor 28 and the output terminal of the first stage driver 13 via the coil 33. ing.

A terminal 12b of the earphone jack 12 is grounded via a coil 34.

Note that the first stage driver 13 acts as a driver for the final stage 14 as will be described later, but is configured so that it can directly drive the earphone 11 by itself.

The coils 33 and 34 form a high impedance for high frequency signals and a low impedance for low frequency signals.

Further, the capacitor 28 functions to guide high frequency signals to the tuner 4 and to prevent low frequency signals from flowing into the tuner 4.

Next, the operation of the circuit shown in FIG. 2 will be explained.

The earphone plug 41 is inserted into the earphone jack 12, and the lead wires 42a and 42b are connected to the terminals 12a and 12b.
When connected to the leads 42 a and 42 respectively, the leads 42 a and 42
b are respectively connected to coils 33 and 34 which have high impedance to high frequency signals.

As a result, the node wires 42a and 42b are placed in a floating state from the ground, and a high frequency signal is induced in the lead wires 42a and 42b.

The high frequency signal induced in the lead wire 42a is connected to the terminal 12a.
and is guided to the tuner 4 via the condenser 28.

The high frequency signal induced in the lead wire 42b is transmitted to the lead wire 42a via the distributed capacitance existing between the lead wires 42a and 42b, and then transferred to the terminal 12.
a and a capacitor 28 to the tuner 4.

Note that when the lead wires 42 a and 42 b are two parallel wires as shown in FIG. 2, the coil 34 may be omitted and the lead wire 42 b may be grounded.

If the lead wires 42 a and 42 b are coaxial wires such as shielded wires, high frequency signals will not be induced in the inner lead wires, so a coil 34 is provided in preparation for such a case, and the lead wires Both 42a and 42b are kept floating from the ground.

The audio output obtained from the tuner 4 is amplified by a driver stage 13, and is supplied from the output end of the driver stage 13 to one end of the earphone 11 via the coil 33, terminal 12a, earphone plug 41, and lead wire 42a.

The other end of the earphone 11 is grounded via a lead wire 42b, a terminal 12b, and a coil 34.

Since the coils 33 and 34 have low impedance to audio signals, the earphone 4 can be driven by the single driver stage 13.

As mentioned above, the lead wires 42a, 42 of the earphone 11
By using b also as an antenna, a dedicated antenna can be made unnecessary.

This is particularly useful when miniaturizing a conventional FM receiver or the like in which a rod antenna or the like is provided, since the rod antenna or the like cannot be miniaturized to a certain extent.

Next, the case where the tuner section 2 and the speaker section 3 are used in combination will be explained with reference to FIG. 1.

In this case, it is possible to listen with earphones 11 or speakers 8.

When listening with the earphones 11, the tuner section 2 described above
Since the same operation is performed as when the is used separately from the speaker unit 3, the explanation will be omitted and the case where listening is performed using the speaker 8 will be described below.

When the tuner section 2 and the speaker section 3 are coupled, electrical connections are made through terminals 9, 10a and 10b.

Terminal 9 is terminal 12C of earphone jack 12 and final stage 1
At the same time, the terminal 12C and the antenna 39 are connected.

Terminals 10a and 10b are for the power line, terminal 10a connects the hot side, and terminal 10b connects the ground side.

The audio signal supplied to the final stage 14 via the terminal 9 is amplified by the final stage 14 and supplied to the speaker 8 .

The high frequency signal induced in the antenna 39 is guided to the terminal 12a via the terminal 9 and the terminal 12C.

At this time, the primary coil of the transformer 24 connected to the antenna 39 forms a high impedance with respect to the high frequency signal, and has the same effect as the coils 12 and 13 described above.

The high frequency signal guided to the terminal 12a is transferred to the capacitor 28
The signal is supplied to the tuner 4 via.

The audio signal obtained from the tuner 4 is guided to a first stage driver 13, and from the output end of the first stage driver 13 is passed through a coil 33, a terminal 12a, and a terminal 9 to a transformer 3.
6.

The other end of the transformer 36 is grounded via a terminal 10b.

At this time, since the coil 33 has a sufficiently low impedance with respect to the audio signal, the output of the first stage driver 13 is supplied to the transformer 36 without being attenuated.

The audio signal supplied to the transformer 36 is amplified by a final stage 14, which will be described later, and is supplied to the speaker 8.

Next, the driver stage 13 and final stage 14 will be explained with reference to FIG.

The first stage driver 13 includes an NPN type transistor 17 and a PN
Complementary-5EP with P-type transistor 18
It is composed of a P (Single Ended 5ushpull) amplification circuit.

Transistor 16 is connected to these transistors 17 and 18.
It constitutes a drive stage for.

Transistor 16 performs class A amplification, and transistors 17 and 18 perform class B or AB class amplification.

Diode 30 provides bias and temperature compensation.

Resistors 21, 22 and 24 are for biasing and capacitors 25 and 27 are coupling capacitors.

The capacitor 26 is a bootstrap capacitor for increasing the apparent load impedance.

This driver stage 13 acts as a driver for the final stage 14, but since it constitutes a power amplifier circuit by itself, it directly drives the earphone 11 connected via the terminal 12a as described above. Is possible.

Further, an input transformer 36 of the final stage 14, which will be described later, is driven by a complementary 3EPP circuit including transistors 17 and 18.

Therefore, the efficiency of power consumption can be increased and the current consumption can be reduced compared to the conventional case where the input quadrature is driven by a class A single amplifier.

Furthermore, since no direct current flows through the transformer 36, the magnetic core of the transformer 36 is not magnetized by direct current, making it possible to improve frequency characteristics (particularly low frequency characteristics).

The final stage 14 is constituted by a conventionally known push-pull amplifier circuit using transformers 36 and 37 as input and output transformers, respectively.

A series circuit of a resistor 23 and a diode 31 connected to the secondary side of the input quadrature 36 is for bias and temperature compensation.

An idling current constantly flows through the transistor 19 and the transistor 20 through a series circuit formed by the resistor 23 and the diode 31.

The transistors 19 and 20 perform class B or class AB amplification.

The push-pull output obtained by the transistors 19 and 20 is supplied to the speaker 8 via the output transformer 37 to drive the speaker 8.

As described above, according to the present invention, since the final stage having the input quadrature is driven by the complementary 3EPP circuit, the efficiency of power consumption can be increased and the current consumption can be reduced.

Furthermore, since no direct current flows through the input quadrature, the magnetic core of the input quadrangle is not magnetized by direct current, and thus frequency characteristics can be improved.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a circuit diagram of a radio receiver, and FIG. 2 is a circuit diagram illustrating an example of how the radio receiver shown in FIG. 1 is used. In addition, in the symbols used in the drawings, 13 is one driver stage, 14 is the final stage, 17.18 is a transistor, and 36
is trans.

Claims (1)

[Scope of utility model registration request] 1. An amplifier circuit comprising: a final stage having an input quadrature; and one driver stage for driving the final stage, the first stage of the driver comprising a complementary 3EPP circuit.