JPH0289487A - Signal amplifying circuit - Google Patents

Abstract

PURPOSE:To select an amplifying unit to be operated by selectively supplying a bias current to the base of the differential amplifying transistors(TR) of the plural amplifying units according to a control signal. CONSTITUTION:A bias supply control circuit 7 is provided, and by supplying a base bias to one of amplifying units 1 and 2 according to the control signal, and preventing the supply to the other one, the amplifying unit 1 or 2 is selected. For example, when the control signal is at a high level, a TR Q9 of a bias supply control circuit 7 is turned off, a TR Q8 is turned on, the amplifying unit 1 is operated, and the amplifying unit 2 is disconnected. In such a constitution, an input side and an output side can be used as matrix circuits to treat component signals in plural forms, and thus, a preferable signal amplifying circuit can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] Regarding a circuit suitable for amplifying a wideband signal such as a high-definition television (HDVS) video signal, in particular a matrix for switching a signal to be amplified. The present invention relates to a signal amplification circuit suitable for use in a circuit.

[Summary of the invention]

It operates by providing multiple amplification units consisting of differential amplification circuits and buffer amplification circuits, and controlling the supply destination of the base bias by taking advantage of the fact that amplification operation can be intermittent by intermittent base bias of the differential amplification circuit. A signal amplification circuit that allows selecting the amplification unit to be used.

[Conventional technology]

For example, in broadcasting equipment, television signals are often handled in the form of component signals. Component signals include R (red), G (green), and B (blue).
There are signals that take the form of , Y (luminance), R-Y, B-Y, or signals that are modified from these, and signals of the same television standard format can be converted by a matrix circuit. It is.

In addition to the matrix circuit, it is often necessary to selectively switch various component video signals or video signals in which luminance signals and color signals are separated.

These technologies include, for example, video tape recorders (VTRs)
It is necessary for connection between devices or for signal processing within devices for recording/playback, program editing, etc.

As an example of the prior art, FIG. 3 shows a matrix circuit that receives two types of component signals and outputs the same type of component signal regardless of which signal is input.

The matrix circuit shown in Fig. 3 can be roughly divided into Y signal or G signal.
A first group is connected from a Y/G input 100 where a signal is input to a Y output 104 which outputs a Y signal, and a R-Y/R input 110 where a R-Y signal or an R signal is input.
A second group that connects to the RY output 114 that outputs the signal, and a third group that connects to the BY output 124 that outputs the BY signal from the BY/B input 120 that receives the BY signal or the B signal. It is composed of the above 3.
Each group has circuits with approximately the same configuration. Each group includes two amplification units for signal amplification (upper, 2, 2, 2, 2, and η, respectively), and a switch is used to select which amplification unit outputs the output. The circuits can be switched by erect, wa and ear, ■, embryo, and yaku, respectively.

By inputting an output switching signal for switching the switch circuit, when the Y, R-Y, and B-Y outputs are input, the amplification unit (1) amplifies them as is.
, υ2, ■, and when G, R, and B signals are input, the amplifier unit (-?-1■, n) converts them into Y, R-Y, and B-Y signals and outputs them, respectively. I am trying to extract the output of .

Here, each of the amplification units includes an emitter input type differential amplifier circuit IA and a buffer amplifier circuit IB as illustrated in FIG. 4, and a bias supply circuit as illustrated in FIG. A bias current of +Vat (base-emitter voltage of transistor Q in FIG. 5) is supplied to the bases of transistors Q, , Qz of amplifier circuit IA.

In the example of the amplification unit shown in FIG. 4, suppose the transistor Q,
, Q2 and the bases A and B are used as input terminals, it operates as an operational amplifier, and the bases A and B become virtual ground.Here, it operates with the emitters C and D of transistors Q= and Qz as input terminals. As a result, the voltage at the output terminal E of the amplification unit is shifted to a higher value by +1. Therefore, the transistor Q in FIG.
A voltage drop of +VIE is caused through the emitter follower. Therefore, transistors Q, , Q7 are mutually connected by using pair transistors.

It is desirable that consideration be given to aligning the following.

Now, when switching signals such as video signals using such a conventional matrix circuit, switch circuits (i, ■,
Relays, analog switch circuits, etc. are required for the terminals (ears, ■, benefits, 马), and the space and cost for arranging them is large, and the burden increases as the number of signal channels (number of switching circuits) increases. There is a problem. Along with this, a problem has arisen that impedes miniaturization in devices that need to record and reproduce in the same recording format no matter which of a plurality of component signals they accept.

In addition, for example, a high-definition television system ([(DV
When amplifying and switching wideband signals such as S) video signals (for example, 30 MHz each for R, G, and B according to the Japan Broadcasting Corporation's studio standard for high-definition signals), the unique characteristics of relays and analog switch ICs (integrated circuits) There is a problem that cannot be ignored. For example, in addition to switch characteristics such as on resistance and signal leakage when off, analog switch ICs must not include nonlinear circuits to prevent cross modulation, and have good differential phase characteristics (DP) and differential gain characteristics (DC). is required. Therefore, the characteristics and circuit scale of individual switch circuits may not be much different from, for example, the amplification unit, or special field effect transistors may be required, making it difficult to implement large-scale ICs including switch circuits. There are difficult problems.

[Problem to be solved by the invention]

In a matrix circuit using a conventional signal amplification circuit, the switch circuit required for switching the output from the amplification unit requires a large amount of installation space, high cost, high frequency characteristics, difficulty in implementing large-scale IC, etc. It is an object of the present invention to solve the above problems and obtain a signal amplification circuit suitable for use in a matrix circuit for amplifying and switching broadband signals.

[Means to solve the problem]

In the present invention, a plurality of amplification units are provided, and each of the plurality of amplification units includes an emitter input type differential amplification circuit and a buffer amplification circuit for buffering and amplifying the output signal of the emitter input type differential amplification circuit. When a bias current is supplied to the base of the differential amplification transistor of the emitter input type differential amplification circuit, the buffer amplification circuit outputs a differential amplification signal, and when the bias current is not supplied to the base of the differential amplification transistor, the buffer amplification circuit outputs a differential amplification signal. The amplifier circuit is configured to exhibit high output impedance without outputting a differential amplification signal, and substantially couples the output terminals of the plurality of amplification units to each other, and connects the amplification differential transistors of the plurality of amplification units. A signal amplification circuit characterized in that an amplification unit to be operated from among the plurality of amplification units can be selected by the control signal by selectively supplying a bias current to the base according to the control signal. do.

The space for installation is small, inexpensive transistors can be used, and integration into the tC is extremely easy.

[Effect]

In the configuration of the present invention, the output terminals of the plurality of amplification units are substantially coupled to each other, and the switch circuits (i, ■, long, river,
This method solves the problems of the prior art.

In the present invention, a bias supply control circuit is provided as a means for switching the output of each of the amplification units in place of the switch circuit, and when the base bias of the emitter input type differential amplification circuit in the amplification unit is intermittently applied, the amplification unit Taking advantage of the fact that the amplification operation of the amplification unit can be intermittent, the amplification unit to be operated can be selected by controlling the supply destination of the base bias.

Since the bias supply control circuit is a simple switch circuit that controls the base bias intermittently, the arrangement (Embodiment) FIG. 1 is a matrix circuit showing an embodiment of the present invention.

There are two basic differences in configuration when comparing the matrix circuit of FIG. 1 with the conventional example of FIG. 3.

The first difference in the configuration is that the conventional switch circuit
■, Remove the long, ear, profit, and Qian, and place on the amplification unit and 2,
The outputs of 11 and 1, 2 and η are coupled after passing through an emitter follower for correcting the voltage shift corresponding to the base bias voltage 2, respectively.

The second difference in the configuration is that the bias supply control circuit 1,
(2) A nail is provided and the transistors Q, , Qz's base A, of the emitter input amplifier circuit lA in FIG.
The structure is such that the base bias supplied to B is intermittent.

FIG. 2 is a circuit diagram showing a main part related to the second difference in the configuration. Compared to the conventional example shown in Fig. 3, in Fig. 2 a bias supply control circuit is provided, which supplies base bias to one of the amplifier units and to the other in response to a control signal. By not supplying on the amplification unit or -? The difference is that - can be selected. For example, when the control signal (output switching signal) b is at a high level, the transistor Q9 of the bias supply control circuit is turned off, the transistor Q is turned on, the amplifier unit operates, and the amplifier unit -? - is rejected.

By adding the bias supply control circuit 1, no new elements are added to the signal path such as I on the amplifier unit (there is no adverse effect on characteristics such as transistor operation).

Rather, in the conventional example, even if the outputs of the amplification unit 1 and the amplification unit 2 are switched by the switch circuit 5.6, -? However, the present invention has the effect of suppressing the circuit current of the amplifier unit in the off state.

In the above, we have described as an example a matrix circuit that handles component signals of multiple formats on the input side and one format on the output side, but both the input and output sides may have multiple formats.
It is clear from the nature of a matrix circuit configured by combining a resistance matrix and a plurality of amplification units that the matrix circuit may handle component signals of one type on the input side and multiple types on the output side.

〔Effect of the invention〕

By implementing the present invention, it is possible to obtain a signal amplification circuit suitable for use in a matrix circuit for amplifying and switching a wideband signal, which does not include a switch circuit in the signal path for switching the output from the amplification unit.

As a result, the switch circuit inserted into the signal path requires a large amount of installation space, increases costs, and degrades high frequency characteristics.
A matrix circuit suitable for switching wideband signals such as video signals of high-definition television systems, for example, can be obtained by solving various problems such as difficulty in implementing large-scale ICs.

By using the matrix circuit, it is possible to miniaturize a device that can input or output a plurality of component signals, and in particular it can contribute to the miniaturization of signal processing circuits for high-definition television signals, which has been difficult in the past.

A%B--Base b---------Control signal (output switching signal)

[Brief explanation of the drawing]

Figure 1 is a matrix circuit showing an embodiment of the present invention, Figure 2 is a circuit diagram showing main parts of the embodiment of the present invention, Figure 3 is a conventional example of a matrix circuit, and Figure 4 is the amplification of Figure 3. A circuit example of the unit, FIG. 5, is an example of the bias supply circuit of FIG. 3. 1, plexus, ■, ■, ■, η--Amplification unit main, soil, ■, ■, profit, illusion 2...-bias supply circuit-5
-1dan,■,■,profit,马-・-・-switch circuit engineer, 1
7.27---Bias supply control circuit IA...-
...-Emitter input type differential amplifier circuit 1B--Buffer amplifier circuit Q, ,Q, ,Q,,Qt,Q, ,Q. ...- Transistor Figure 3 Conventional example of matrix and supination Circuit diagram showing the main parts of this Komei's big sale example 2nd Circuit example of the amplifier unit in Figure 3 4th Figure 3 Noise switch Figure 5, column A

Claims (1)

[Claims] A plurality of amplification units are provided, each of the plurality of amplification units includes an emitter input type differential amplification circuit and a buffer amplification circuit that buffers and amplifies the output signal of the emitter input type differential amplification circuit, When a bias current is supplied to the base of the differential amplification transistor of the emitter input type differential amplification circuit, the buffer amplification circuit outputs a differential amplification signal, and when the bias current is not supplied to the base of the differential amplification transistor, the buffer amplification circuit outputs a differential amplification signal. The buffer amplifier circuit is configured to exhibit high output impedance without outputting a differential amplification signal, and substantially couples the output terminals of the plurality of amplification units to each other, and the differential amplification transistors of the plurality of amplification units. By selectively supplying a bias current to the base of the circuit according to the control signal, an amplification unit to be operated from among the plurality of amplification units can be selected by the control signal. .