JPS60236309A - Acoustic device - Google Patents

Abstract

PURPOSE:To use a frequency characteristic variable circuit as a power amplifier by connecting a single-ended push-pull complementary circuit to an operational amplifier for frequency said variable circuit. CONSTITUTION:A single-ended push-pull complementary circuit 29 which is used as an output part of a power amplifier is connected to an output terminal 7 of an operational amplifier 4 for a frequency characteristic variable circuit. The frequency converting negative feedback is applied to a negative input terminal 6 of the amplifier 4 via resistances 15 and 14. When variable resistors 11-13 are actuated toward (a), the attenuation is performed since BPFs 8-10 are connected to a positive input terminal 5 of a differential amplifier at the first stage. While the amplitude is carried out when resistors 11-13 are moved toward (b). In such a way, the frequency characteristic variable circuit can also be used as a power amplifier.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a variable frequency characteristic circuit (a type of tone control, generally called a graphic equalizer) for stereo equipment, tape recorders with radios, etc. (The number of points varies depending on each product.) This relates to audio equipment in general.

(Configuration of conventional example) Figure 1 shows an example of a circuit diagram of a conventional audio device.
The variable frequency characteristic circuit 18 and the power amplifier 19 were configured independently. Various circuits are used as the variable frequency characteristic circuit 18, but here the first stage differential amplifier (the output stage can be either an emitter follower or a single-ended goose-sol circuit).

As an example, a circuit using an operational amplifier 4 with a band), a band) filter 8°9.10, and special variable resistors 11, 12, and 13 whose resistors are cut in the center is shown as an example. . Furthermore, although three variable frequency points are shown, any number of variable frequency points is possible by increasing the number of bandpass filters and variable resistors. When the variable resistor is operated in the a direction, each bandpass filter is connected to the positive input terminal 5 of the operational amplifier 4, so it is not attenuated, and when the variable resistor is operated in the b direction, it is connected to the negative input terminal 6. This is the direction of amplification. Other signs include
1 is an input terminal, 2 is a resistor that determines the characteristics during attenuation, 3 is a buffer resistor, 5, 6, and 7 are the positive input terminal, negative input terminal, and output terminal of the operational amplifier 4, respectively, and 14 is the amplification characteristic. The resistors 15, 16 and 17 are the resistors and capacitors that form a negative feedback circuit, and the values of the resistors 15 and 17 determine the gain of the variable frequency characteristic circuit 18.
is a speaker.

FIG. 2 is a frequency change characteristic diagram of a conventional variable frequency characteristic circuit. As is clear from FIG. 1, the variable frequency characteristic circuit 18 is composed of an operational amplifier 4 that is completely independent from other circuits. In addition, since the four-hour amplifier 19 also has an independent circuit configuration, the number of parts is large and the circuit as an audio device becomes complicated. Furthermore, frequency characteristic variable circuit 1
8 and power amplifier 19 each have a voltage gain, unless phase correction is applied to both circuits, abnormal phenomena such as parasitic oscillation may occur. There was a problem in that the shock sound etc. at the time was further amplified by the war amplifier, making it considerably louder.

(Object of the invention) The present invention is intended to solve the above-mentioned problems, and its purpose is to combine a frequency characteristic variable circuit and an i9 with a simple configuration.
To provide an audio device that can also be used as a power amplifier and operates stably.

(Structure of the Invention) The present invention has an operational amplifier having a differential amplifier in the first stage and a single-ended Gussi quadruple complementary circuit in the output stage, and a number of pantone filters and bandpass filters. The output of the circuit is configured by combining variable resistors so that the frequency characteristics can be varied to any desired characteristic, and there are also 51 single-ended push nor combinary circuits that have performance according to the motherboard power output. The circuit is configured such that the operational amplifier for the variable frequency characteristic circuit can also be used as a voltage amplification section of the putter amplifier, by connecting the output terminal to negative feedback for variable frequency characteristics. By simplifying the circuit, reliability can be improved and costs can be reduced, and performance can also be improved, such as by reducing shock noise when the power switch is turned on and off.

(Description of Embodiment) FIG. 3 is a circuit diagram of an embodiment showing the configuration of the audio device of the present invention.

Here, the same parts as in FIG. 1 are given the same numbers and their explanation will be omitted. The output terminal 7 of the operational amplifier 4 for the variable frequency characteristic circuit is connected to a single-ended semi-complementary circuit (hereinafter abbreviated as output section) 29', which is generally used as the output section of a power amplifier. Then, negative feedback for frequency variation is sent from the output through a resistor 15.14 in the calculation output unit 29, where 22 is a temperature compensation transistor, and 20.21 is the temperature compensation transistor 22.
23 is a resistor for balancing the DC potential of the output section 29, 24 and 26 are drive transistors of NPN type and PNP type, respectively, forming a congruentary circuit, and 27 and 28 are transistors for driving. As an output transistor, the temperature compensation transistor 22
The idling current of the output transistor 27.28 is determined by the ratio of the two resistance values of the bias resistor 20.21. Also, 25 and 36 are the load resistances of the drive transistors 24 and 26, and 30.31 and 32 are the load resistances of the drive transistors 24 and 26. Resistors and capacitors for bootstrazzo, 33 and 34
are resistors and capacitors for phase correction.

The gain of this circuit is determined by the ratio of the resistors 15 and 17, the amount of attenuation when changing the frequency characteristic is determined by the resistor 14, and the amount of amplification is determined by the resistor 2. The larger the resistors 2 and 14 are, the larger the amount of increase or decrease becomes. Variable resistor 11° Since each bandpass filter is connected to the positive input terminal 5 of the first stage differential amplifier in the amplifier 4, it is on the attenuation side, and when moved to the b side, it is connected to the negative input terminal 6, so this The phase is opposite to the output signal of the circuit and becomes the amplification side. In this way, even though this circuit has two functions: variable frequency characteristics and power amplification, it can be regarded as an ordinary circuit in terms of operation, and the circuit is significantly simplified compared to conventional circuits. Therefore, it is possible to improve reliability and reduce costs by reducing the number of parts.

Furthermore, since the operational amplifier 4 provides all of the voltage gain, and the output section 29 only amplifies the current and does not amplify the voltage, the shock noise caused by turning the power switch on and off can be made very small. In Fig. 3, the output section 29 is a discrete system and all transistors are used, but there are other commercially available products in which the entire output section 29 is integrated into an IC, or two Darlington-connected transistors are packaged into one. Their use can further promote circuit simplification.

FIGS. 4 and 5 show other embodiments of the output section 29 according to the present invention.

Figure 4 shows that the power output is 2 watts, y! □This shows an example in which the output part 29 does not need to be connected to Darlington, and only one stone can be used for both the upper and lower parts.

FIG. 5 shows that while the output section 29 shown in FIG. 3 uses a quasi-connolimentary circuit, it may also be a pure complementary circuit.

(Effects of the Invention) As explained above, the present invention can provide an audio device with an extremely simple configuration and a stable operation frequency characteristic variable circuit and a power-up function, and furthermore, an operational amplifier 4 and an output section 29 can be provided. Using a common IC further enhances this effect, and can be expected to improve reliability and reduce costs by reducing the number of parts.Additionally, a variable frequency characteristic circuit can be used to reduce power supply.

Even if a shock sound is generated due to ion-off, the output section 29
Since the voltage is not amplified, it is very small, and experimental results show that when 10B2 r-Bz is kept at a constant voltage, it is almost non-existent.
This sufficiently solves the problems of the conventional example.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of a circuit diagram of a conventional audio device;
The figure is a frequency change characteristic diagram of a conventional variable frequency characteristic circuit, FIG. 3 is a circuit diagram of an embodiment showing the configuration of the audio device of the present invention, and FIGS. 4 and 5 are other than the output section 29 in the present invention. It is a figure showing an example of. 1... Input terminal, 2... Resistor that determines characteristics during attenuation, 3... Buffer resistor, 4... Operational amplifier, 5...
Positive side input terminal of operational amplifier, 6... Negative side input terminal of operational amplifier, 7... Output terminal of operational amplifier, 8, 9.1
0... Pantone e filter, 11, 12, 13...
・Variable resistor, 14... Resistor that determines amplification characteristics, 15
, 17... Resistor for negative feedback circuit, 16... Capacitor for negative feedback circuit, 20, 21.23... Bias resistor,
22...Temperature compensation transistor, 24.26...
Drive trunk star, 25.36...Load resistance,
27゜28... Output transistor, 29... Single end, Doppler Seagle complementary circuit (output section), 3'0, 31... Bootstrap resistor, 32... Bootstrap capacitor, 33・
...Capacitor for phase correction, 34... Resistor for phase correction, 35... Speaker. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] An operational amplifier with a differential amplifier in the first stage and a single-ended Zossy pull complementary circuit in the output stage,
By combining several band pass filters and variable resistors corresponding to the number of band/gas filters, the output of the circuit is configured such that the frequency characteristics can be varied to any desired characteristic. By connecting yet another single-ended push-pull complementary circuit with corresponding performance and applying negative feedback for variable frequency characteristics from this output terminal, the operational amplifier for the variable frequency characteristic circuit is connected. - An acoustic device characterized in that it is configured to double as a voltage amplification section for a Guwaanzo.