JPS6325768Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is configured so that the power supply current of the amplifier is constant regardless of the input signal.
The purpose is to eliminate the influence of power supply impedance on the amplifier.

Generally, the power supply current of an audio amplifier changes depending on the level of the input signal, so that a fluctuation in the power supply voltage occurs in proportion to the magnitude of the power supply impedance. Therefore, in the past, efforts have been made to reduce the power supply impedance over a wide band in order to minimize this power supply voltage fluctuation and suppress signal distortion. There is a limit to this reduction due to the impedance of the metal, and the economic burden is also large.

The present invention improves the above drawbacks by providing a current change suppression circuit equipped with a constant current source different from the amplifier's power supply to maintain the amplifier's power supply current constant and prevent signal distortion from occurring. This will be explained in detail below using an embodiment shown in FIG.

In FIG. 1, 3 has a non-inverting input terminal 1, an inverting input terminal 2, a non-inverting output terminal 4 which provides an output in phase with 1, and an inverting output terminal 5 which provides an output with the opposite phase to 1. The differential amplifier is a balanced differential amplifier having a balanced load whose power supply current does not change depending on the input signal, and the terminals 4 and 5 are connected to the bases of transistors 7 and 8 constituting the differential amplifier, respectively.
The emitters of transistors 7 and 8 are connected in common and biased from +B power supply terminal 35 via resistor 9. A diode (or diode-connected transistor) 11, resistors 12 and 14, and a transistor 13 constitute a current mirror load,
The base of transistor 13 is connected to the collector of transistor 7, and the collector of transistor 13 is connected to the collector of transistor 8 via bias circuit 10. Transistor 25,2
9, resistors 26 and 28 constitute a SEPP complementary output circuit, and the bases of the transistors 25 and 29 are connected to the collectors of transistors 13 and 8, respectively, and the output signal is output from the output terminal 27 via the negative feedback circuit 6. is negatively fed back to the inverting input terminal 2 of the amplifier 3. In an amplifier with such a configuration, a resistor 1 constituting a current mirror load
Between the connection point 15 of 2 and 14 and the -B power supply terminal 26,
The first to third resistors 17 are connected between the collector terminal 24 of the transistor 25 constituting the SEPP complementary output circuit and the -B power supply terminal 26, and between the collector terminal 30 of the transistor 29 constituting the output circuit and the +B power supply terminal 35. , 21, and 32 are connected to each other. Current changes in each of the resistances are detected by detection circuits 18, 22, and 33, respectively, and control circuits 19, 23, and 24 connected to the detection circuits.
are the resistors 17, 21,
32 current changes are suppressed. In FIG. 1, the portion constituted by this detection circuit and control circuit is shown as first to third current change suppression circuits 16, 20, and 31.
An example of the first and second current change suppression circuits 16 and 20 is shown in FIG.
An example of this is shown in FIG. In FIGS. 2 and 3, terminals corresponding to those in FIG. 1 are given the same numbers, and parts having the same functions are given the same numbers. Resistors 17, 21, and 32 are connected between terminal 15 and terminal 36, between terminal 24 and terminal 36, respectively.
and a resistor for detecting a current change between the terminal 35 and the terminal 30. The base of the transistor 38 is connected to the corresponding terminals of the terminals 15, 24, and 30 via the resistor 37, and the resistors 17, 21, and 32 are connected to each other. Amplify the voltage change that occurs. The collector of the transistor 38 is grounded via a constant current source 39 and connected to the base of a control transistor 40.
The collector of the transistor 40 is grounded, and the emitter is connected to corresponding terminals 15, 34, and 30. In order to simplify the explanation, the current change suppression circuits 16 and 20 are shown simultaneously in FIG. 2, and the same functional parts in FIG. 2 and FIG. Current change suppression circuit 16, 2
This does not mean that the transistors, constant current sources, and resistors of 0 and 31 are the same, and they do not need to be the same.

Next, the operation will be explained. When a signal is applied to the input terminal 1, the power supply current of the amplifier 3 and the current flowing through the emitter bias resistor 9 of the differential amplifier composed of transistors 7 and 8 do not change depending on the configuration; The current is 2 times the change in the collector current of transistor 7 due to the current mirror load.
Change twice. Furthermore, the current changes at the terminals 30 and 24 are determined by the load including the negative feedback circuit connected to the output terminal 27 and the output voltage generated at the output terminal 27. Therefore, circuit 1 related to the present invention
If 6, 20, and 31 are not present, this changing current is
The current flows through the +B power supply terminal 35 and the - power supply terminal 36, and as long as the power supply connected to the terminals 35 and 36 has a finite impedance, the changing current causes fluctuations in the power supply voltage. However,
Considering the case where the circuit shown in FIG. 2 is connected as the circuit 16, a current change in the resistor 17 is detected as a voltage change at both ends, and this change is amplified by the transistor 38 and applied to the base of the control transistor 40. be done. Now, assuming that the current changes in the direction of increasing current, the transistor 38
The collector potential of the transistor 40 decreases, the base-emitter voltage of the transistor 40 decreases, and the emitter current of the transistor 40 decreases. At this time, the collector of the transistor 38 is connected to the constant current source 39, so if the base current of the transistor 40 is sufficiently small compared to the current value of the current source 39 and can be ignored, the collector current of the transistor 38 is Therefore, the voltage between its emitter and base and the voltage across the resistor 37 also hardly change, and the varying current is transferred to the resistor 3 by the transistor 40 so that the voltage across the resistor 17 becomes constant.
7. Furthermore, when the current change in the resistor 17 changes in a direction in which the current decreases, the transistor 38 operates in the opposite manner to the above, and the transistor 40
The emitter current of resistor 17 increases and the current of resistor 17 is kept constant. The above description also applies to the circuits 20 and 31, so the currents flowing through the resistors 21 and 32 are also constant. As a result, +B power supply terminal 3
The current flowing through the power supply terminals 35 and 36 will be maintained at a constant value regardless of the input signal voltage applied to the input terminal 1, even if the power supply connected to the power supply terminals 35 and 36 Even if there is impedance, its influence can be removed. Further, in the amplifier according to the present invention, even if an abnormal current change occurs at the terminals 15, 24, 30 and each control transistor 40 of the current change suppression circuit 16, 20, 31 becomes uncontrollable, the resistor 17, 21 , 32 is selected to be less than 1/10 of the value of the resistor 37, the resistor 1 is connected between the terminals 15 and 36, between the terminals 24 and 36, and between the terminals 35 and 30.
7, 21, and 32 are connected to each other, and has a feature that does not affect the signal amplification operation of the amplifier shown in FIG.

This invention is based on its operating principle as shown in Figures 1 and 2.
It is clear that similar operation can be obtained by reversing the polarity of the transistor, diode, and power supply in FIG. In addition, the resistor 37 in FIGS. 2 and 3 is
This is a resistor for limiting the base current of the transistor 28 when an excessive voltage occurs across the resistors 17, 21, and 32, and can be omitted if there is no risk of this happening. The constant current source 39 can be replaced with a resistor if some variation in the current flowing through the resistors 17, 21, and 31 is allowed.

As described above, according to the present invention, the power supply current of the amplifier can be made constant regardless of the input signal, and the influence of the impedance of the connected power supply can be eliminated. Further, since the current change suppression circuit does not have any influence on the characteristics of the active elements of the amplifier, it can be designed without considering the relationship with the active elements of the amplifier, and therefore is easy to manufacture.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an amplifier according to the present invention, and FIGS. 2 and 3 are circuit diagrams showing an embodiment of a current change suppression circuit forming a part of the amplifier. 3...Balanced differential amplifier, 7, 8, 13, 2
5, 29, 38, 40...transistor, 17,
21, 32... First to third resistors, 11... Diode, 15, 24, 30... Connection terminal, 16,
20, 31...first to third current change suppression circuits,
18, 22, 33... Current change detection circuit, 19,
23, 24...control circuit, 27...output terminal, 3
5...+B power supply terminal, 36...-B power supply terminal, 3
9... Constant current source.

Claims (1)

[Claims for Utility Model Registration] A differential amplifier having a current mirror load;
In an amplifier that operates with two positive and negative power supplies and is configured with a SEPP complementary output circuit, a connection point between the emitter resistor of a transistor constituting a current mirror load and a series circuit of a diode and a resistor connected to the base of the transistor;
A first resistor is connected between the power supply, a second resistor is connected between the negative power supply terminal of the SEPP complementary output circuit and the negative power supply, and a second resistor is connected between the positive power supply terminal of the SEPP complementary output circuit and the negative power supply. A third resistor is connected between the positive power source, and a first current change suppression circuit is connected to the first resistor.
A second current change suppression circuit is connected to the second resistor, and a third current change suppression circuit is connected to the third resistor, and the current change suppression circuit is configured to respond to a voltage change across the corresponding resistor. A detection circuit that detects a change in current in the resistor, and a constant current source are provided, and a current that is controlled by the output of the detection circuit and keeps the voltage across the resistor constant is supplied from the constant current source to the detection circuit. and a control circuit for suppressing current changes in the resistor.