JPH0628384B2 - Amplifier circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an amplifier circuit that can obtain a wide frequency band and high output, and is particularly suitable for use in video equipment such as various display devices, measuring equipment, and the like.

[Background technology]

As a video device, a television receiver is generally known, but in recent years, many display devices that display a desired image on a picture tube based on a video signal and a color signal supplied from an electronic computer have become popular. It's coming. In the above video equipment, an amplifier circuit having a high frequency band and a high amplification degree, that is, a so-called video amplifier is required to amplify a high frequency video signal and a color signal. In addition, the television receiver has an introductory color television (Showa 57, 7, 2
6th edition 1st printing issue, publisher Tokyo Denki University Press, PP1
87-140) is used.

By the way, the frequency band of the video amplifier used in the television receiver is about 4,5 MHz as known to those skilled in the art.

However, a display device used as a data processing terminal device of an electronic computer is required to have an image with high resolution and high definition. For this reason, there are cases where there are 1000 or more scanning lines, and the shadow mask of the picture tube (cathode ray tube) is also miniaturized.

Then, in order to display an image with high resolution and high definition, it is necessary to finely adjust the electron beam of the picture tube,
It was revealed by the study of the present inventors that a high output video amplifier is required for this purpose.

It is also clear from the study by the present inventors that the frequency response must be accelerated in order to process data at a high speed, and a video amplifier having a wide frequency band (for example, 200 MHz) is required for this purpose. Became.

On the other hand, electronic devices, not limited to display devices, generally tend to be made smaller and lighter, and circuits constituting the electronic devices have been formed of semiconductor integrated circuits.
When the video amplifier is formed into a semiconductor integrated circuit, a PNP transistor having a large base accumulated charge and a low cutoff frequency is not suitable for the video amplifier. Since a large current is passed to obtain a high output, special consideration is given to heat dissipation. Is necessary, etc.

In addition, the so-called three primary color signals of at least a red (R) signal, a green (G) signal, and a blue (B) signal are often supplied to the video amplifier as input signals, but in order to reduce interference between the above signals, a cross signal is generated. It was also found that it is necessary to improve the talk characteristics. Further, the above three primary color signals R, G, B
Since the DC is supplied to the video amplifier with DC blocking, it was also found that a stable image can be displayed if the so-called pedestal level fluctuation is set according to the input level.

Then, the present inventors have studied the above technical problems and technical trends, and in forming a semiconductor integrated circuit, a semiconductor integrated circuit technology called an ultrafine process device is suitable, We have found that a video amplifier, which is integrated into a semiconductor integrated circuit, is provided for each of the three primary color signals to reduce heat generation and improve crosstalk characteristics.

Further, by forming an NPN transistor by using the above ultrafine process device and forming a video amplifier,
I noticed that a wide frequency band could be obtained. Furthermore,
We have also developed a circuit technology for obtaining high output without providing a so-called power amplifier circuit in the semiconductor integrated circuit. Further, with regard to the setting of the pedestal level, the level of the output signal is detected during the period when the pedestal level appears, and a circuit technology capable of stabilizing the pedestal level of the video amplifier by the level is developed.

[Object of the Invention]

An object of the present invention is to provide an amplifier circuit having a wide frequency band, capable of obtaining a high output, and having a good crosstalk characteristic.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[Outline of Invention]

To briefly describe the outline of the invention disclosed in the present application,
It is as follows.

That is, each color signal that is an input signal is supplied to an amplifier circuit configured in an individual semiconductor integrated circuit, and each amplifier circuit is provided with a wide frequency band amplification means, a plurality of voltage-current conversion means, and each voltage-current. The present invention achieves the object of the present invention to obtain an amplifier circuit having a wide frequency band, high output, and good crosstalk characteristics, by configuring the output current of the conversion means by a current combining means. .

〔Example〕

An embodiment of an amplifier circuit to which the present invention is applied will be described below with reference to FIGS. 1 is a block diagram of a display device to which the amplifier circuit is applied, FIG. 2 is a block diagram showing the circuit configuration of the amplifier circuit, FIG. 3 is a circuit diagram of the amplifier circuit, and FIG. 4 is a circuit operation. 5 is a waveform diagram for explaining FIG.

The feature of this embodiment is that an amplifier circuit (applied as a video amplifier) to which R, G, and B three primary color signals are supplied is formed by a semiconductor integrated circuit by an ultrafine process device,
A wide frequency band, high output, and good crosstalk amplification are performed.

First, the overall structure of the display device will be described with reference to FIG.

An electronic calculator 1 supplies color signals representing the three primary colors of R, G, B to the D / A converter 2 by digital signals. From the D / A converter 2, analogized R, G,
B primary color signals are obtained, and the lines 1 ₁ , 1 ₂ and 1 are respectively obtained.
It is supplied to the amplifier circuits 11, 12, and 13 via ₃ .

Each of the amplifier circuits 11 to 13 is formed by an individual semiconductor integrated circuit (hereinafter referred to as IC). This is because when the amplifier circuits 11 to 13 are formed on the same semiconductor substrate, the three primary color signals R, G, and B are prevented from leaking to the amplifier circuits adjacent to each other and the crosstalk is deteriorated.

Further, by forming each of the amplifier circuits 11 to 13 in an individual IC, the heat generated from one IC is reduced, so that there is an advantage that heat dissipation becomes easy.

The _three primary color signals R, G, and B amplified by the amplifier circuits 11 to 13 are supplied to the cathodes K ₁ , K ₂ , and K ₃ of the picture tube 3 and have colors corresponding to the levels of the _three primary color signals R, G, and B. The image of is displayed.

By the way, each of the amplifier circuits 11 to 13 is formed of an individual IC, but actually has the same circuit configuration. Therefore, in the description of the circuit configuration of each of the amplifier circuits 11 to 13, the amplifier circuit 11 provided for amplifying the R signal will be described for convenience of description.

The circuit configuration of the amplifier circuit 11 will be described with reference to FIG. The circles surrounding the numbers in the IC indicate external connection terminals.

Reference numeral 21 denotes a buffer amplifier, which is provided with two amplifiers A and B. This circuit configuration is, for example, for increasing the added value of the display device, such as displaying the two images in an overlapping state. Basically, it may be one amplifier. The R signal is supplied to the amplifier A via the DC blocking capacitor C ₁ .

A switch circuit 22 is provided to selectively transmit the output signals of the amplifiers A and B to the subsequent stage. The switch circuit 22 is composed of two switches S ₁ and S ₂ , but the switching of the _two switches S ₁ and S ₂ is performed by the control signals Va and Vb. Both of the switches S ₁ and S ₂ can be turned on, and only one of them can be turned on.

The resistor R ₁ provided outside the IC sets the gain of the amplifier circuit 11 to a desired value, but this sets the basic value, and the fine adjustment of the gain is performed by the gain control circuit of the next stage. Two
It is performed by 4.

The gain control circuit 24 is a gain circuit 24 that controls the voltage gain.
a and a drive circuit 24b for driving the gain circuit 24a. The drive circuit 24b compares the reference voltage Vref ₁ with the control signal Vc to obtain the gain circuit 24b.
Control the voltage gain of a.

Reference numeral 25 denotes a voltage-current conversion circuit, which is composed of a plurality of current mirror circuits, that is, eight current mirror circuits connected in parallel in this embodiment. According to this circuit configuration, even if the output current of one current mirror circuit is a small current, the current flowing through the line 1a corresponding to the current combining means in the present invention is proportional to the number of current mirror circuits. It becomes a large current.

The current flowing through the line 1a is the output circuit 26 of the next stage.
It is the one that draws the electric current from.

The output circuit 26 performs current-voltage conversion and supplies an output voltage V ₀ obtained as a voltage drop of the load resistor R1 to the cathode K ₁ , and a part of the output voltage V ₀ obtains the feedback signal Vf. It is also supplied to the variable resistor VR.

That is, the output voltage V ₀ includes the R signal and the synchronizing signal, and there is a pedestal period between them. Looking at the input terminals of the amplifiers A and B, since the R signal is supplied as an AC component, a DC bias must be set, but the voltage level thereof needs to be set to a pedestal level. The feedback signal Vf is obtained for this purpose, but it is only necessary to actually feed back the pedestal level. The detection circuit 27 will be described below.
Is provided to achieve the above object.

The detection circuit 27 includes a comparator 27a that obtains a pedestal level by comparing the reference voltage Vref ₂ and the feedback signal Vf, a switch S ₃ that is switched to an ON state while the pedestal level is obtained, and a pedestal level that is not held during the pedestal level period. It is composed of a capacitor C ₂ for switching, an amplifier 27b, and a control circuit 27c that switches the switch S ₃ to the ON state in the pedestal period based on the control signal V _D. The control signal V _D input to the 14th terminal is a signal that changes to a high level during the pedestal period and is supplied in synchronization with the pedestal period of the R signal.

The output voltage Vp of the amplifier 27b is a voltage corresponding to the pedestal level, and sets the bias voltage of the amplifiers A and B to a predetermined voltage level via the resistors Ra and Rb.

Although the amplifier circuits 12 and 13 have the same circuit configuration as that of the amplifier circuit 11, for convenience of illustration, terminals 5 to 10 and external parts connected to the terminals are not shown. Omit it.

Next, with reference to FIGS. 3 and 4, the circuit operation of the amplifier circuit 11 will be described in more detail. Since the amplifiers A and B have the same circuit configuration, common reference numerals are given to the respective circuit components, and ‘′’ is given to the amplifier B. Further, since the control circuits 23a, 23b and 27c also have the same circuit configuration, common reference numerals are respectively attached to the circuit components, and the control signals 23b and 27c are denoted by ′ and ″.

The power supply voltage Vcc ₂ supplied to the 21st terminal is output circuit 26
It is lower than the power supply voltage Vcc ₁ supplied to the. Two ground lines, that is, a terminal 22 and a terminal 23, are provided. This is because the current flowing through the voltage-current circuit 25 is a large current, and the GND level is prevented from fluctuating. This is the purpose. That is, since the ground line in the IC has an inductance component, when a current including a high frequency component flows, a voltage drop occurs and the GND level fluctuates, which eventually contributes to the fluctuation of the image. However, by adopting the IC structure as in this embodiment, the above phenomenon can be reduced.

In the amplifier A, transistor Q ₁ is an input transistor, a resistor in response to the voltage level of the R signal R _11,
It controls the current flowing through R ₁₂ and the transistor Q ₂ .

Since the transistors Q _2, Q ₃ form a current mirror circuit, so that also the current flowing through the transistor Q ₃ to Q _5, resistors R _13, R ₁₄ are controlled by the transistor Q _1.

On the other hand, the resistance R _15, R _16, R ₁₇ and transistor Q _6, Q ₇ also constitute a current mirror circuit, which is to define the current flowing through the transistor Q _8, Q _9.

If the R signal goes high and the current flowing through the transistors Q ₁ and Q ₂ increases, the current flowing through the transistor Q ₃ also increases, and the base current of the transistor Q ₈ decreases correspondingly. Then, the current flowing from the transistor Q ₈ to the transistor Q ₇ decreases, and the reduced amount is absorbed from the diode-connected transistor Q ₉ . Therefore, the voltage drop across the resistor R ₁₈ becomes large, and this is supplied as the output voltage to the next stage via the switch S ₁ .

In this case, the control circuit 23a controls the transmission of the output voltage as follows.

When the control signal Va is at high level, the emitter voltage of the transistor Q ₁₁ becomes high level, so that the transistor Q ₁₁ is turned off and the power source Vcc ₂ is applied to the transistor Q ₁₂ via the resistor R ₂₁ . Then, the transistor Q ₁₄ operates in the ON state, the base current is supplied to the transistor Q ₁₅ , and the transistor Q ₁₅ operates in the ON state. The transistor Q
₁₃ is for preventing the base voltage of the transistor Q _{15 from} rising above the collector voltage, and the resistor R ₂₂ is for supplying a bias voltage to the transistor Q ₁₅ .

In this way, when the transistor Q ₁₅ is turned on, the current flowing through the resistor R ₁₈ increases and the voltage drop amount also increases. In this case, the base voltage of the transistor Q ₂₁ , which operates as the switch S ₁ , is lowered, so that it is turned off and transmission of the output voltage of the amplifier A is blocked.

On the other hand, when the control signal Va is switched to the low level, the transistor Q ₁₁ is turned on, current flows through the power supply Vcc ₂ , the resistor R ₂₁ , and the transistor Q _11, and the collector voltage of the transistor Q ₁₂ drops. , Transistors Q _{13 to} Q
All ₁₅ are off. Therefore, the resistor R _18, the base current of the current and the transistor Q ₂₁ suction by the transistor Q ₇ flows, the transistor Q ₂₁ is turned on. In other words, the switch S ₁ is closed and the output voltage of the amplifier A is transmitted.

The above circuit operation is similarly performed for the amplifier B and the control circuit 23b. Thus, the line 1 _11, the control signals Va, by for varying the level of Vb, the amplifier A, one of the output voltages of B, or the combined voltage of both output voltage is selectively appears that. The amplifier B operates similarly to the amplifier A, and the control circuit 23b operates similar to the control circuit 23a.

Further, the ground lines of the amplifiers A and B and the line of the constant voltage circuit 100 described later are grounded via the 23rd terminal separately from the other ground lines. This is because when the level fluctuation of the GND line occurs especially in the first stage, it is amplified in the latter stage as it is, and the fluctuation of the image becomes large.
This is done to reduce this decrease.

Then, the output voltage appearing on the line _{11 1} is supplied to the gain circuit 24a via the two resistors R and R ₁ .

Incidentally, 31 is a constant current circuit, the resistor R _31, R ₃₂ supplies a bias voltage to the transistor Q _31, to stabilize the base current supplied to the transistor Q ₃₂ ~ transistor Q ₃₈ via the transistor Q ₃₁ . The resistors R ₃₃ and R ₃₄ define the current flowing through the transistor Q ₃₂ ,
Resistor R ₃₅ supplies the bias voltage. The transistors Q ₃₃ , Q ₃₇ , and Q ₃₈ are composed of N transistors, and a desired amount of current can be obtained in proportion to the number of transistors, that is, in proportion to the emitter area.

Here, the gain circuit 24a will be described. The emitter voltage Vx of the transistors Q ₄₂ and Q ₄₃ is equal to that of the amplifiers A and B.
Determined by the output voltage of the transistors Q ₄₁ and Q ₄₄
The emitter voltage Vy of V is determined by the transistor Q ₃₅ and the resistor R. Although the resistors R ₃₆ and R ₃₇ are load resistors, the output voltage is obtained as the voltage drop of the resistor R ₃₇ .

Output voltage of the gain circuit 24a, the bias voltage Vs of the voltage Vx of the transistor Q ₄₁ to Q _44, is controlled by the difference voltage between Vt, the bias voltage Vs, Vt setting is performed by the drive circuit 24b.

Resistors R ₄₁ , R ₄₂ Transistors Q ₅₁ , Q ₅₂ , Q _{53 The} base resistors R of the transistors Q ₅₂ , Q ₅₃ form a current mirror circuit, and determine the current flowing through the transistors Q ₅₄ , Q _{55 and the} like. Further, the resistors R ₄₃ and R ₄₄ supply a bias voltage to the transistor Q ₅₄ , and at the same time, the voltage Vref ₁₁ is also supplied.

On the other hand, resistors R ₆₁ and R ₆₂ , transistors Q ₇₁ and Q ₇₂ ,
The emitter resistors R of Q ₇₃ , the transistor Q ₇₂ , and the transistor Q ₇₃ form a current mirror circuit, and regulate the current flowing through the transistors Q _{61 to} Q ₆₄ on the emitter side. The collector side of the transistors Q _{61 to} Q ₆₄ is regulated to a predetermined current by the transistors Q ₆₅ and Q ₆₆ . The base voltage of the transistors Q ₆₅ and Q ₆₆ is maintained at a predetermined voltage level by the constant voltage circuit 100 composed of the resistors R ₇₁ and R ₇₂ and the transistors Q ₈₁ , Q ₈₂ and Q ₈₃ .

The voltage Vs determined by the current flowing through the transistors Q ₆₁ and Q ₆₂ and the voltage Vt determined by the current flowing through the transistors Q ₆₃ and Q ₆₄ are determined by the voltages Vref ₁₁ and Vref _{12 as} described below. It is determined.

That is, the voltage Vref ₁₂ is supplied to the bases of the transistors Q ₆₁ and Q ₆₂ via the resistor R ₄₅ , while the resistor R ₄₆ to
It is supplied to each base of the transistors Q ₆₃ and Q ₆₄ via R ₄₈ . Therefore, in this state, the resistors R _{46 to} Q
The voltage drop of ₄₈ causes the transistors Q ₆₁ and Q _{62 to have} a high level.

However, the transistor Q ₅₄ is because it is the on state, the transistor Q _55, current mirror circuit constituted by Q ₅₆ is operated, the transistors Q _57, Q _56, via a resistor R ₄₉ output current. Since the current flowing through the transistor Q ₅₃ is regulated to a predetermined amount, the output current flows through the resistor R ₄₈ to the bases of the transistors Q ₆₃ and Q ₆₄ . Therefore, the current flowing through the transistors Q ₆₄ and Q ₆₅ also increases, and the voltage Vt correspondingly increases. Therefore, the resistors R _{45 to} R ₄₇ function as a so-called attenuator, the switching operation of the attenuator is performed by the voltage Vref ₁₁ , and the voltages Vs and Vt correspond to the attenuator output.

In the gain circuit 24a, transistors Q ₄₁ by a voltage difference Vs-Vy is turned on, current flowing through the resistor R ₃₇ is determined, which the transistor Q ₄₃ is also turned on simultaneously by the voltage difference Vt-Vx. The resistor R _37, the current of the sum of the transistor Q _41, Q ₄₃ flows, a voltage drop is enlarged by the resistor R _37. That is, the voltage Vs, Vt is multiplied by the amplification. Resistor R ₃₆ , R
_In order to prevent the transistors Q ₄₁ to Q ₄₄ from being saturated (preventing the Early effect), ₃₇ has different resistance values. Further, as is apparent from the above circuit operation, the gain circuit 24a also performs a current-voltage conversion operation.

The output voltage of the gain circuit 24a is supplied to the voltage-current conversion circuit 25 in the next stage, and the offset voltage adjustment circuit 31 is also associated with this circuit.

In the adjusting circuit 31, the resistors R ₈₁ and R ₈₂ supply a bias voltage to the transistors Q ₉₁ and Q ₉₂ , and the resistors R ₈₃ and R ₈₂ .
₈₄ supplies a bias voltage to the transistor Q ₉₃ . When the resistor VR ₂ is controlled, the bias voltage of the transistor Q ₉₃ changes, so that the currents flowing through the transistors Q ₉₁ , Q ₉₂ and the resistor R ₈₆ are controlled, and the voltage drop amount of the resistor R ₈₆ is adjusted. This voltage drop is used for offset adjustment of the voltage-current conversion circuit 25.

Next, the circuit operation of the voltage-current conversion circuit 25 will be described.
However, this circuit includes seven sets of voltage-current conversion circuits 25a-2
The circuit 25a will be described because it is composed of 5h and has the same circuit configuration.

The power supply Vcc ₃ is supplied to the transistors Q ₁₁₁ and Q ₁₁₃ , and the current flowing through the resistors R ₉₁ and R ₉₂ transistors Q ₁₁₂ and Q ₁₁₃ is controlled by the voltage of the gain circuit 24a. Since the transistors Q ₁₁₂ , Q _114, and Q ₁₁₅ form a current mirror circuit, by controlling the base currents of the transistors Q _{112 to} Q ₁₁₅ by the transistor Q ₁₁₃ ,
The base current of transistor Q ₁₁₆ is also controlled. At this time, the transistors Q ₁₁₇ and Q ₁₁₈ are controlled by the adjustment voltage.
Is controlled, and the base current of the transistor Q ₁₁₆ is finely adjusted.

The transistor Q ₁₁₆ supplies a base current to the transistors Q ₁₂₁ and Q ₁₂₂ which form the current mirror circuit.
The amount of current changes according to the output voltage of the gain circuit 24a. Therefore, the current flowing from the output circuit 26, the line 1a through the transistor Q ₁₂₂ , and the resistor R ₉₇ changes in accordance with the output voltage of the gain circuit 24a, and further the voltage level of the R signal.

For convenience of description, assuming that the sink current of one voltage-current converter circuit 25a is Ia, the same amount of current is sucked by each of the voltage-current converter circuits 25b to 25h. As a result, the current drawn from the output circuit 26 through the line Ia has a current amount of 8Ia.

Then, the current of 8 Ia is converted into the voltage-current conversion circuit 25 from the power supply Vcc ₁ through the resistor R ₁ , the N-channel MOS transistor Qa for eliminating the influence of the output capacitor, and the transistor Qb whose base is AC-grounded. Sucked by Then, the output voltage V ₀ is obtained as described above, and this is supplied to the cathode K _{1 of the} picture tube. The resistor R ₁₀₀ VR constitutes a feedback circuit for clamping the pedestal level, and the feedback signal Vf having a waveform as shown in FIG. 4 is supplied to the detection circuit 27. The pedestal level corresponds to P in the figure.

Next, the circuit operation of the detection circuit 27 will be described.

The resistor R ₁₁₁ , the transistors Q _{131 to} Q ₁₃₈ , and the resistor R connected to the bases of the respective transistors Q _{131 to} Q ₁₃₆ are
It constitutes a constant current circuit.

The transistors Q ₁₄₁ and Q _{142 form} a comparison circuit 27a,
The resistors R ₁₂₁ and R ₁₂₂ are for obtaining the reference voltage Vref ₂ .
Transistor Q _143, Q ₁₄₄ is clamper, the bias voltage resistors R _123, R _124, is supplied by the transistor Q _145.

When pedestal level P is detected by the comparator circuit 27a, the transistor Q ₁₄₆ is driven, current is supplied to the switch S _3.

On the other hand, the transistors Q ₁₄₇ and Q constituting the switch S ₃ are
₁₄₈ includes transistors Q ₁₄₉ , Q ₁₅₁ , Q _{152 and a} resistor R _126.
Although the base current is supplied from the constant current circuit configured by, the opening / closing control of the switch S ₃ is performed by the control circuit 27c.

The control signal V _D is at a low level corresponding to the period of the pedestal level P, and is kept at a high level in other periods. When the control circuit V _D is at the high level, the circuit operation as described in the control circuit 23a is also performed in the control circuit 27c, and the transistor Q
₁₅ ″ works in the on state.

On the other hand, when the control signal V _D is at the low level, the transistor Q ₁₅ ″ is turned off. When the transistor Q ₁₅ ″ is off, the transistors Q ₁₅₃ and Q ₁₅₄ provided as level shifters are turned on. There is no current sink through and the transistor Q ₁₄₇ turns on,
Transistor Q ₁₄₈ turns off.

Therefore, the pedestal level of the output signal of the comparison circuit 27a is charged in the capacitor C ₂ provided as a storage element via the resistor R ₁₂₇ , and the level is stored.

In contrast to the above operation, when the transistor Q ₁₅ ″ is in the on state, the transistor Q ₁₄₈ is in the on state and the resistor R ₁₂₇ ,
The capacitor C ₂ is discharged through the transistors Q ₁₄₈ , Q ₁₃₇ and the resistor R. This operation is repeated, and the DC voltage corresponding to the level of the feedback signal Vf is supplied to the transistor Q ₁₆₁ which constitutes the comparison circuit via the resistor R ₁₂₈ . The bias voltage of the transistor Q ₁₆₂ is held at a predetermined voltage level by a constant voltage circuit composed of a resistor R ₁₃₂ transistor Q _{163 and the} like. Therefore, the current flowing through the transistors Q ₁₆₄ and Q ₁₆₂ changes depending on the charging voltage of the capacitor C ₂ , and the change level is the feedback signal V.
Corresponds to the level change of f.

Since the transistors Q ₁₆₄ , Q ₁₆₅ , Q ₁₆₆ and the resistor R _{135 form} a current mirror circuit, the current change is supplied from the transistor Q ₁₆₆ to the transistors Q ₁ and Q ₁ ′ via the resistors Ra and Rb. The base current changes. That is, the DC bias of the amplifiers A and B is maintained at a predetermined level value by the pedestal level of the R signal.
Therefore, even if the R signal is supplied by the AC component as described above, the fluctuation of the image displayed on the picture tube can be reduced.

[Effect]

The present invention relates to a voltage amplification circuit for amplifying an input signal, a plurality of voltage-current conversion circuits for converting a voltage level change of an output signal of the voltage amplification circuit into a current change, and a plurality of these voltage-current conversion circuits.
An amplifier circuit is constituted by a current synthesizing means for synthesizing the output currents of the current converting circuit to obtain a high output current, and an output circuit for obtaining a high output based on the output currents synthesized by the current synthesizing means. Since the voltage-current conversion circuit and the current synthesizing means are formed as an integrated circuit on one semiconductor substrate, and the output circuit is configured and connected separately from the semiconductor integrated circuit, it is possible to realize a high voltage inside the semiconductor integrated circuit. There is an effect that a high-output amplifier circuit can be obtained without providing a withstand voltage element, the amount of heat radiation in the case of a semiconductor integrated circuit can be reduced, and deterioration of characteristics and shortening of life can be prevented.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention. Yes.

For example, more buffer amplifiers may be provided. Also,
The same applies to the control circuit 23.

Further, the number of voltage-current conversion circuits can be arbitrarily changed according to the purpose of use.

[Field of application]

In the above description, the case where the invention made mainly by the present inventors is applied to a video amplifier which is a field of application which is the background of the invention has been described, but the invention is not limited thereto, and a wide band amplifier circuit such as an oscilloscope is used. It can be used for measuring instruments that need it.

Further, it can also be used in a communication device using digital signals.

It may also be used for audio equipment.

[Brief description of drawings]

1 is a block diagram of a display device showing an embodiment of the present invention, FIG. 2 is a block diagram of an amplifier circuit applied to the display device, and FIG. 3 is a circuit diagram of the amplifier circuit. 4 shows a waveform diagram for explaining the circuit operation. 1 ... Computer, 2 ... D / A converter, 3 ... Picture tube, 11 ... Amplification circuit, 21 ... Buffer amplifier, 22 ...
Switch circuit, 23 ... Control circuit, 24 ... Gain control circuit, 25 ... Voltage-current conversion circuit, 26 ... Output circuit,
27 ...... detection circuit, 1a ...... signal combining means, Vf ...... feedback signal, Vd, Va, Vb ...... control signal, R ...... input signal, V ₀ ...... output voltage, Q ₁ to Q ₁₆₆ ...... transistor ,
R _{1 to} R ₁₃₇ ... Resistor, Ic ... Semiconductor integrated circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenkichi Yamashita Inventor Kenkichi 52-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Plant (72) Inventor Kazuo Kato 4026, Kuji-cho, Hitachi City, Ibaraki Stock Company Hitachi Research Laboratory, Hitachi (72) Hideo Sato 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-61-274410 (JP, A)

Claims (1)

[Claims] 1. A voltage amplification circuit for amplifying an input signal, a plurality of voltage-current conversion circuits for converting a voltage level change of an output signal of the voltage amplification circuit into a current change, and a plurality of the plurality of voltage-current conversion circuits. Of the voltage-current conversion circuit, to obtain a high output current, and (4) an output circuit that obtains a high output based on the output current synthesized by the current synthesizing means. The voltage amplifying circuit, the voltage-current converting circuit, and the current synthesizing means are formed as an integrated circuit on one semiconductor substrate, and the output circuit is configured and connected separately from the semiconductor integrated circuit. An amplifier circuit characterized in that.