JPH0215381Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a SEPP output circuit used as an output circuit for various amplifiers such as equalizers, flats, tone filters, and main amplifiers in audio equipment.

As shown in Figure 1, the conventional SEPP circuit consists of transistors Q ₁ to _{Q 4} , resistors R ₁ to R ₄ , constant current load 1, and bias circuit 2, and input voltage Vi is applied to the collector of negative transistor Q _2. - Has configurations added between bases. A model of an amplifier using this conventional output circuit is shown in FIG. In Figure 2, A is the amplifier and R _L is the output terminal OUT in Figure 1.
Z ₁ is the impedance of the earth circuit, and C ₁ and C ₂ are the pass capacitors.

In the circuit shown in Fig. 2, when a sine wave is input as the input voltage Vi, the power supply currents i ₁ , i ₂ and the ground current i when the load R _L is heavy and the output stage is in class B operation. ₃ (combined current of i ₁ and i ₂ ) are shown in A, B, and C, respectively. Furthermore, the waveforms of the power supply currents i ₁ and i ₂ during class A operation are as shown in d and e.
Now, if we focus on the current _i3 flowing to the ground, the circuit in FIG. 2 can be simplified as shown in FIG. 3.

As is clear from FIG. 3, even if amplifier A supplies an undistorted output V ₀ , the voltage V′ ₀ across the load R _L is V′ ₀ = R _L /R _L +Z ₁ V ₀ . The voltage V′ ₀ and thus the current flowing through the load are strongly influenced by the impedance Z ₁ . Here, if the impedance Z ₁ has high linearity, there will be little problem, but if it contains non-linear components such as contact resistance or pattern impedance, or if the impedance is high, the voltage V′ ₀ may be distorted and the frequency Characteristics may deteriorate. This results in a deterioration in sound quality. Conventionally, this required countermeasures such as inserting a bus line made of steel plate or the like.

In addition, in this conventional circuit, as _shown in FIG _. 4, currents i ₄ ,
Since _i5 flows to ground, there was a problem that the sound quality changed depending on the characteristics of the pass capacitor.

An object of the present invention is to provide an SEPP output circuit with a simple circuit configuration that can make the impedance component described above appear to be zero, and that can reduce changes in sound quality due to the characteristics of the pass capacitor.

To achieve this purpose, the SEPP output circuit of the present invention detects the collector or emitter current of the output transistor of the SEPP output circuit, and flows the same current as the current of the transistor on the positive power supply side from the ground to the negative power supply side. The device is characterized in that the same current as the current of the transistor on the negative power supply side is caused to flow from the positive power supply side to the ground.

The details of the present invention will be explained below with reference to embodiments shown in the drawings. Figure 5 shows an embodiment of the present invention, and Q ₅
~ _Q10 is a transistor, _R5 ~ _R16 are resistors, _D1 , _D2 ,
D ₃ and D ₄ are transistors Q ₇ , Q ₈ , Q ₉ , and
A diode for correcting the base-emitter voltage of _Q10 , 1 is a constant current load, and 2 is a bias circuit.

In the circuit shown in Figure 5, when the input voltage Vi is excited to the positive side, transistor _Q5 turns on,
Collector current flows. and resistance R ₅ and D ₁
The output of the detection means consisting of transistor Q ₇
increases, the transistor Q 10 is controlled by the output of the detection means consisting of the resistor R ₁₂ and D ₄ , and the transistor Q ₁₀ is controlled from ground to the resistor R ₁₅ , the transistor Q ₁₀ ,
The current flowing through resistor _R16 to the negative supply side also increases. Here, by selecting resistance values such that R ₅ =R ₁₆ and R ₉ =R ₁₂ , the collector currents of transistors Q ₅ and Q ₁₀ become equal. Similarly, when the input voltage is excited to the negative side, current flows through transistor Q ₆ , and by setting R ₈ = R ₁₃ and R ₁₀ = R ₁₁ , the collector current of transistors Q ₆ and Q ₉ (positive power supply side (current flowing from to ground) will be equal.

This current relationship is shown in FIG. In Fig. 6, the current i ₆ flowing through the transistor Q ₅ passes through the load R _L inserted between the output terminals CUT in Fig. 5, flows to the negative power supply side via the transistor Q ₁₀ , and flows through the transistor Q ₆ . Current i ₇ flows from the positive power supply side through transistor Q ₉ load R _L into said transistor Q ₆ , and none of the current flowing through load R _L flows to ground.

Since the currents i ₆ and i ₇ have the same absolute value and are out of phase by 180°, the currents during class A operation and class B operation are as shown in A and B in FIG. 7, respectively. In FIG. 7, a is a positive power supply current, b is a single power supply current, and c is a ground current. That is, during class A operation, no alternating current flows through either the power source or the ground. Furthermore, it can be easily understood from the schematic diagram of FIG. 8 that even if a pass capacitor is attached, no current flows to the ground from the current waveform during class B operation.
That is, the current i ₈ passing through the pass capacitors C ₁ and C ₂ does not pass through the ground.

The above is summarized as shown in FIG. 9th
As can be seen from the figure, the impedance of the earth Z ₁
No alternating current flows through , therefore Z ₁ can be considered to be 0.

Figure 10 is an amplifier that is an application example of the SEPP output circuit shown in Figure 5, 3 is the SEPP output circuit in Figure 5, 4 and 5 are first stage and intermediate stage amplifier circuits, respectively.
Z ₂ and Z ₃ are the impedances that constitute the feedback circuit, and Z _L
is the load.

FIG. 11 shows another embodiment of the present invention, in which transistors Q ₅ and Q ₆ in FIG. 5 are replaced by inverted Darlington-connected transistors.
Q ₁₁ and Q ₁₃ and Q ₁₂ and Q ₁₄ are used, and
In this case, the emitter currents of transistors Q ₁₁ and Q ₁₂ are detected and the same currents are caused to flow through transistors Q ₁₀ and Q ₉ .

As described above, according to the present invention, even if a non-linear or high impedance exists in the ground circuit, the amplifier will not be adversely affected at all. That is, impedance is not transformed into output distortion. In many cases, this output distortion causes audible discomfort as a muddy sound, and the present invention eliminates this muddying and provides clear sound. In addition, when the output stage operates in class A mode, no alternating current flows through the power supply, so distortion and noise due to the impedance of the power supply do not occur, and the sound quality is not affected, which also improves the sound quality. Helpful. In addition, conventionally, a pass capacitor is inserted between the power supply and the ground to reduce ripples in the power supply, but according to the present invention, even if this pass capacitor is inserted, the current flowing through it is Since it cannot flow to earth, the sound quality will not be affected. Furthermore, in the past, a low impedance pass line such as a steel plate was provided in order to avoid the influence of the impedance of the ground circuit, but according to the present invention, these are no longer necessary, which helps to reduce costs. In addition to the above-mentioned effects, the fact that it can be easily realized with a simple circuit configuration without requiring any additional circuits other than the signal path has a great effect on productivity and cost reduction.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional SEPP output circuit.
Figures 2 to 4 are model diagrams explaining the problems, Figure 5 is a circuit diagram showing an embodiment of the SEPP output circuit of the present invention, and Figure 6 is a diagram showing the selection of the resistance of the circuit in Figure 5. Figure 7 is a waveform diagram explaining the operation of the circuit in Figure 5. Figure 8 is a model diagram showing the current flow obtained as a result. Figure 8 is a waveform diagram explaining the operation of the circuit in Figure 5. A model diagram explaining that no current flows, Figure 9 is a model diagram explaining the overall current flow of an amplifier using the circuit in Figure 5, and Figure 10 is an example of an application of the circuit in Figure 5. FIG. 11 is a circuit diagram showing another embodiment of the present invention. D ₁ - _{D 4} ... Diode, Q ₁ - _{Q 14} ... Transistor, R ₁ - _{R 14} ... Resistor, 1 ... Constant current load, 2
...Bias circuit.

Claims (1)

[Scope of utility model registration request] one consisting of first and second transistors;
In an amplifier in which the SEPP circuit operates with two positive and negative power supplies, a first current detection means connected between the first transistor and the positive power supply;
a fourth transistor controlled by the output of the first current detection means so that the same current as that of the first transistor flows from the load to the negative power supply; and a connection between the second transistor and the negative power supply. a third current detecting means connected between the second current detecting means and a third transistor controlled so that the same current as that of the second transistor flows from the positive power supply to the load by the output of the second current detecting means; one end of the load is connected to a connection point between the first and second transistors, and the third transistor, the fourth transistor, and ground are connected to the other end of the load; When the input signal is a positive half cycle, current flows from the positive power supply to the negative power supply through the first transistor, the load and the fourth transistor, and when the input signal is a negative half cycle, the current flows through the first transistor, the load and the fourth transistor. The present invention is characterized in that the current is caused to flow from the positive power source to the negative power source through the transistor No. 3, the load, and the second transistor so that the signal current does not flow into the ground.
SEPP output circuit.