JPH07162243A - Wide-band direct-current amplifier - Google Patents

Abstract

PURPOSE:To reduce an operating current for a signal of a DC low-speed component and to obtain a driving current for a capacitive load for a signal of a high-speed component. CONSTITUTION:New differential amplifiers formed by combining transistors(TR) 11 and 12, and 41 and 42 which differ in conductor characteristics from each other and a DC feedback amplifier composed of Trs 25 and 55 are constituted to obtain a transmission line which determines a DC component. To provide a transmission line for the high-frequency component, PNP Trs 22 and 52 are put in operation while the emitters are grounded by capacitors 21 and 51, and capacitors 15 and 16, and 45 and 46 are connected while signals have the same polarity so that balanced outputs are obtained through the operation of the capacitors, thereby reducing the DC operating current and also improving high frequency characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide band DC amplifier used for output amplification of an oscilloscope, and in particular, taking advantage of the characteristics of transistors having different conductor characteristics, it is possible to simultaneously realize DC amplification and high frequency characteristics with a simple structure. A wideband DC amplifier that can be improved.

[0002]

2. Description of the Related Art Generally, by grasping the characteristics of the rising and falling waveforms of a pulse signal, the transmission characteristics from low frequencies to high frequencies can be estimated.

Here, the case where the signal rises in the positive direction is defined as the positive polarity, and the case where it falls in the negative direction is defined as the negative polarity.

Further, when driving the capacitance of the circuit, it is preferable to select the circuit so that the base input of the NPN transistor is a positive polarity signal and the base input of the PNP transistor is a negative polarity signal because of the characteristics of the conductor characteristics of the transistor. This is a more suitable way to use, and this will be referred to as the active direction.

In an oscilloscope, a vertical and horizontal output amplifier supplies a signal voltage required for vertical and horizontal deflection of a cathode ray tube. However, the cathode ray tube deflection electrode is a capacitive load, and it is inevitable when a high speed signal is required. Large high-speed current must be supplied.

Conventionally, desired results have been obtained by combining transistors having different conductor characteristics with an amplifier used for this type of purpose.

FIG. 3 is a circuit diagram of a conventional amplifier, which is composed of a DC coupling feedback means for inputting a balanced signal and an AC amplifier. Such amplifiers are used as horizontal output amplifiers in oscilloscopes.

The horizontal signal of the oscilloscope is called a sweep signal, and its waveform is a sawtooth wave, and is usually divided into a sweep period for deflecting the cathode ray tube beam from left to right and a blanking period for deflecting the cathode ray beam from right to left start point. To be When the speed of the sweep signal becomes high, the sweep signal output required for this is obtained, so that a large current of the capacitive load can be supplied.

A conventional horizontal output amplifier will be described below with reference to FIG. In this horizontal output amplifier, the balanced input / output circuit with respect to the horizontal electrodes of the cathode ray tube is vertically symmetrical, and therefore the circuit will be described in the state of being divided into upper and lower parts.

In FIG. 3, ei is a balanced input signal (sweep signal), and the upper half of this horizontal output amplifier has transistors 65, 70, 90, 92 and resistors 63, 67, 7 respectively.
1, 72, 74, 75, 76 and capacitors 73, 7
7, 79, the output terminal 78 of which is connected to one horizontal electrode of the cathode ray tube 94.

The lower half of the horizontal output amplifier is composed of transistors 69, 80, 91 and 93 and resistors 64, 68 and 8.
1, 82, 84, 85, 86 and capacitors 83, 8
7, 89, the output terminal 88 of which is connected to the other horizontal electrode of the cathode ray tube 94. Incidentally, 66 is a common emitter resistance of the transistors 65 and 69.

The upper half of the transistor 65, the transistors 70 and 90, and the resistor 72 constitute a DC coupled feedback amplifier for amplifying DC and low frequency components, and the transistor 92 and the capacitors 73 and 77 amplify high frequency components.

The lower half transistor 69, the transistors 80 and 91, and the resistor 82 constitute a DC coupled feedback amplifier for amplifying DC and low frequency components, and a transistor 93 and capacitors 83 and 87 for amplifying high frequency components.

[0014]

In the conventional amplifier as described above, when the input terminal 61 is a positive polarity signal during the sweep period, the transistors 65, 70 and 92 are in the active direction,
It is convenient for amplifying high frequency signals. Further, when the polarity is negative in the blanking period, only the transistor 90 is in the active direction, but the fall tends to be delayed.

On the other hand, when the input terminal 62 is a negative signal during the sweep period, the transistors 80 and 91 are in the active direction, which is convenient for amplifying a high frequency signal. Further, when the polarity is positive in the blanking period, only the transistor 93 is in the active direction, but the transistors 80 and 91 are inactive,
The fall operation tends to be slow.

Further, in order to make the sweep time faster, it is necessary to make not only the rising of the balanced signal but also the falling operation. In addition, when the falling characteristic is important like the rising edge like the vertical signal,
This circuit is difficult to handle.

The present invention is to solve the above-mentioned conventional problems, in which the operating current is reduced with a DC low speed component signal,
It is an object of the present invention to provide a wide band DC amplifier capable of obtaining a driving current of a capacitive load for a high speed component signal.

[0018]

In order to achieve the above object, the present invention connects the emitters of a pair of transistors having conductor characteristics different from each other through a parallel circuit of a resistor and a capacitor, and Of one of the transistors having different conductor characteristics from each other, by applying one of the balanced signals to the base of the first amplifier to take out the output from the collector through the capacitor, and grounding the base of the other transistor to take the directly connected output from the collector. The emitters are connected via a parallel circuit of a resistor and a capacitor, the other of the balanced signals is applied to the base of the one transistor, the output is taken from the collector through the capacitor, and the base of the other transistor is grounded. Second amplifier that directly outputs the output from the collector and a pair of transistors with different conductor characteristics. And a collector connected directly to the capacitive load of the transistor, the one transistor is provided with a feedback resistor, and the emitter of the other transistor is grounded via a capacitor. And a pair of transistors having different conductor characteristics from each other, the collectors of the transistors are directly connected to a capacitive load, the one transistor is provided with a feedback resistor, and the emitter of the other transistor is connected to a capacitor. A fourth amplifier which is grounded via the output of the first amplifier, and the direct output of the first amplifier is input to the base of one of the transistors of the fourth amplifier, and also through the capacitor of the first amplifier. The output thus extracted is applied to the base of the other transistor of the third amplifier to directly connect the second amplifier. The force is input to the base of one of the transistors of the third amplifier, and the outputs taken out through the capacitor of the second amplifier are applied to the bases of the other transistors of the fourth amplifier to output each other. Are configured so that they are in phase as balanced amplifiers.

[0019]

With the above structure, the present invention can form a transmission line for determining a DC component and a transmission line for a high frequency component, which enables DC operation and improves high frequency characteristics.
Moreover, the operating current is reduced with the signal of the DC low-speed component,
With the signal of the high-speed component, the drive current of the capacitive load of the cathode ray tube can be effectively extracted without waste.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit configuration diagram when the wide-band DC amplifier according to the present invention is applied to a horizontal output amplifier of a cathode ray tube of an oscilloscope.

In FIG. 1, 1 and 2 are input terminals,
A balanced signal ei corresponding to a sweep signal is applied between the input terminals 1 and 2. Input resistors 3 and 4 are connected between the input terminals 1 and 2 and the ground.

11, 41 are NPN transistors, 12,
42 is a PNP transistor, the emitters of the transistors 11 and 12 are directly connected through a parallel circuit of a resistor 9 and a high frequency characteristic improving capacitor 10, and the collectors of the transistors 11 and 12 are load resistors 13 and 1
It is connected to the + E power source or the −E power source via 4.
Further, the bases of the transistors 12 are connected to bias setting resistors 5 and 6 and a capacitor 8.

The emitters of the transistors 41 and 42 are directly connected via a parallel circuit of a resistor 39 and a high frequency characteristic improving capacitor 40, and the collectors of the transistors 41 and 42 are + E via load resistors 43 and 44.
Connected to power supply or -E power supply. Further, the base of the transistor 42 has resistors 35 and 36 for bias setting.
And a capacitor 38 are connected.

22, 52 are PNP transistors, 25,
55 is an NPN transistor, the collectors of the transistors 22 and 25 are directly connected, the emitter of the transistor 25 is connected to the + Eb power source through the resistor 20 for determining the emitter current, and the high speed signal is connected between the collector and ground. Is connected to a capacitor 21 for supplying a necessary current, and its base is connected via a capacitor 15 for transmitting a high frequency signal to the transistor 11 in the preceding stage.
Connected to the collector. Reference numerals 18 and 19 are base resistors that set the base voltage of the transistor 22.

The feedback resistor 24 is connected between the collector and the base of the transistor 25, and the base of the feedback resistor 24 is connected to the preceding stage via a parallel circuit of a DC voltage converting resistor 47 and a high frequency signal bypass capacitor 46. It is connected to the collector of the transistor 42.

The collectors of the transistors 52 and 55 are directly connected, the emitter of the transistor 55 is connected to the + Eb power source through the resistor 50 for determining the emitter current, and a high-speed signal is applied between the collector and ground. A capacitor 51 for supplying a necessary current is connected, and its base is a capacitor 4 for high frequency signal transmission.
It is connected via 5 to the collector of the transistor 41 at the preceding stage. Reference numerals 48 and 49 are base resistors for setting the base voltage of the transistor 52. Also, the transistor 55
A feedback resistor 54 is connected between the collector and the base of the same, and its base is connected to the collector of the transistor 12 at the preceding stage through a parallel circuit of the DC voltage converting resistor 16 and the high frequency signal bypass capacitor 17. ing.

Reference numeral 23 is an output terminal connected to the collectors of the transistors 22 and 25, and 53 is an output terminal connected to the collectors of the transistors 52 and 55. Both output terminals 2
Both horizontal electrodes of the cathode ray tube 57 of the oscilloscope are connected between 3 and 53. Reference numerals 26 and 56 are capacitors connected between the output terminals 23 and 53 and the ground.

Next, the operation of this embodiment configured as described above will be described. In FIG. 1, input terminals 1, 2
2 (a) and 2 (b) show the relationship between the polarity of the balanced signal ei applied to and the time.

First, the case of amplifying the low frequency component of the balanced signal including the direct current will be described. In an amplification system including the transistors 11 and 12, when a balanced signal having the polarity shown in FIG. 2 is applied to the base of the NPN transistor 11, the emitter of the transistor 11 supplies the balanced signal to the emitter of the PNP transistor 12 through the resistor 9. At this time, since the base is grounded, a signal in phase with the emitter appears at the collector, and this signal is supplied to the transistor 55 of the next stage through the resistor 17.

The NPN transistor 55 of the next stage which receives the above signal has the emitter grounded and the collector and the base of the resistor 5.
A DC feedback amplifier circuit connected by 4 is constructed, and P
The base voltage of the NP transistor 52 is resistors 48 and 49.
The collector current is determined by the resistor 50, and the output is taken out from the collectors of the PNP transistor 52 and the NPN transistor 55. Therefore, considering all paths of the signal, that is, from the input terminal 1 to the output terminal 53, since all are configured by direct coupling, all low frequency signal components including direct current supplied from the input terminal 1 are transmitted to the output side. To be done. This means that the input DC voltage dominates the DC output voltage.

Next, an amplification system including the transistors 41 and 42 will be described. When a balanced signal of the polarity shown in FIG. 2B is applied to the base of the NPN transistor 41, it is supplied from the emitter of the transistor 41 through the resistor 39 to the emitter of the PNP transistor 42. At this time, since the base is grounded, a signal in phase with the emitter appears at the collector. This signal is supplied to the next-stage transistor 25 through the resistor 47.

Here, the NPN transistor 25 constitutes a DC feedback circuit in which the emitter is grounded and the collector and the base are coupled by the resistor 24, and the base voltage of the PNP transistor 22 is the resistors 18 and 19 and the collector current thereof. Is determined by the resistor 20 and PN
The output is taken out from the collectors of the P transistor 22 and the NPN transistor 25. Therefore, considering the entire path of the signal, that is, from the input terminal 2 to the output terminal 23, since all are configured by direct coupling, all low frequency signals including direct current supplied from the input terminal 2 are transmitted to the output side. It

As described above, the balanced signal of the low frequency component including the direct current supplied to the input terminals 1 and 2 is amplified and output to the output terminals 23 and 53 to which the cathode ray tube 57 is connected, as shown in FIG.
It will be supplied to (d) as a balanced output.

Next, the case of transmitting a high frequency signal will be described. When a positive balanced signal is applied to the input terminal 1, the NPN transistor 11 is in the active direction and its collector is negative, so that a high-frequency signal is generated by the capacitor 1.
It is supplied to the base of the PNP transistor 22 via 5. At this time, since the emitter of the PNP transistor 22 is grounded by the capacitor 21, this collector,
That is, the output terminal 23 becomes positive and the capacitor 26
Is charged rapidly.

On the other hand, the emitter signal of the transistor 11 is supplied to the emitter of the PNP transistor 12 through the resistor 9 and the capacitor 10. At this time, since the base is grounded, the transistor 12 is in the active direction and the collector has a positive polarity. As a result, the signal appearing at the collector is supplied to the base of the transistor 55 through the resistor 17 and the capacitor 16.

Accordingly, the transistor 55 is activated and the collector, that is, the output terminal 53 has a negative polarity, so that the capacitor 56 is rapidly discharged.

As described above, when a positive signal is applied to the input terminal 1 in the high frequency signal, the signal passes through the transistor 11 and the capacitor 15 and then to the transistor 22.
Supplied to the base of. At this time, since the emitter of the transistor 22 is grounded by the capacitor 21, the current flows from the output terminal 23 to the ground through the capacitor 26.

Next, signal transmission when a high-frequency balanced signal is input to the input terminal 2 side will be described.

When a positive polarity balanced signal is applied to the input terminal 2, the transistor 41 is in the active direction and the collector thereof is in the negative polarity, so that a high frequency signal is supplied to the base of the PNP transistor 52 through the capacitor 45. . At this time, the emitter of the transistor 52 is the capacitor 51.
Since it is grounded at, the collector, that is, output terminal 5
3 becomes positive and the capacitor 56 is charged rapidly.

On the other hand, the emitter signal of the transistor 41 is supplied to the emitter of the PNP transistor 42 through the resistor 39 and the capacitor 40. At this time, since the base of the transistor 42 is grounded, its collector becomes positive in the active direction. As a result, the signal appearing at the collector is supplied to the base of the NPN transistor 25 through the resistor 47 and the capacitor 46. As a result, the transistor 25 is activated and its collector has a negative polarity, so that the capacitor 26 is rapidly discharged.

As described above, in the high frequency signal, when a positive signal is applied to the input terminal 2, the signal is applied to the base of the transistor 52 through the transistor 41 and the capacitor 45. At this time, since the emitter of the transistor 52 is installed by the capacitor 51, current flows from the output terminal 53 through the capacitor 56.

FIG. 2 shows a time relationship and a polarity relationship between the balanced input signal and the output signal. (A) at the input terminals 1 and 2,
When a balanced signal of the polarity shown in (b) is input, the output terminals 53 and 23 are correspondingly input to (c) and (d) of FIG.
A balanced signal of the polarity shown in appears.

In particular, when the rise and fall of the signal, which is a high frequency component, affects the circuit,
When the input signal of (a) is of positive polarity, the balanced output signals of outputs (c) and (d) produce high-speed positive and negative polarity signals which coincide in time.

When the input signal of (b) is of positive polarity, the balanced output signals of outputs (c) and (d) produce high-speed positive and negative polarity signals which coincide in time.

Further, summarizing the paths of high-speed currents flowing through the respective transistors constituting the final stage, the capacitance, and the ground, when the input signal of FIG. Rise to the condenser 2
6 is charged, and the transistor 55 is active via the ground and the capacitor 56 and is in the saturation direction. Therefore, the current flows from the grounding point of the emitter through the capacitor 21 and the transistor 22 to make a round.

When the input signal of FIG. 2B has a positive polarity, the transistor 52 rises in the active direction due to the satiety direction to charge the capacitor 56, and the transistor 25 is activated via the ground and the capacitor 26. , Because of the saturation direction, the capacitor 51, the transistor 52 from the ground point of the emitter
The electric current goes through once through.

The above path is a closed circuit, which can handle a required large current only at high speed instead of direct current at low speed, and comprehensively superimposes high frequency components including direct current from the output terminals 23 and 56. The balanced signal thus obtained will be obtained.

[0049]

According to the present invention, by combining transistors having different conductor characteristics, the operating current is reduced for signals of direct current and low speed components, and the drive current of the capacitive load of the cathode ray tube for signals of high speed components. Therefore, it has a high-speed component and effectively supplies the necessary positive and negative drive currents to the Braun tube, which is a capacitive load, and amplifies balanced input signals of opposite polarities. It is possible to provide a wideband DC amplifier suitable for an output amplifier of an oscilloscope.

Further, according to the present invention, since the capacitive load is driven by utilizing the transistors having different conductor characteristics with a small number of constituent parts, the drive load in the input stage can be reduced and the operation effective for the output is performed. Can be made.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a wide band DC amplifier according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between polarities of input signals and output signals and time in the present embodiment.

FIG. 3 is a circuit diagram of a conventional DC amplifier.

[Explanation of symbols]

 1 and 2 input terminals 3 and 4 resistors 11 and 41 NPN transistors 12 and 42 PNP transistors 9 and 39 resistors 10 and 40 capacitors 13 and 14, 43 and 44 resistors 17 and 47, resistors 16 and 46 capacitors 15 and 45 capacitors 25 and 55 NPN transistor 24, 54 resistor 22, 52 PNP transistor 18, 19, 48, 49 resistor 20, 50 resistor 21, 51 capacitor 26, 56 capacitor 57 cathode ray tube

Claims (1)

[Claims] 1. A pair of transistors having different conductor characteristics are connected between emitters through a parallel circuit of a resistor and a capacitor, and one of the balanced signals is applied to the base of the one transistor to form a capacitor from the collector. A first amplifier which takes out an output via the base, grounds the base of the other transistor, and takes out a direct connection output from the collector;
The emitters of transistors having mutually different conductor characteristics are connected via a parallel circuit of a resistor and a capacitor, the other of the balanced signals is applied to the base of the one transistor, and the output is taken out from the collector through the capacitor, and the other of the A second amplifier for grounding the base of the transistor and taking out a direct output from the collector; and a pair of transistors having conductor characteristics different from each other. The collectors of the transistors are directly connected to be connected to a capacitive load. One of the transistors has a feedback resistor, has a third amplifier in which the emitter of the other transistor is grounded via a capacitor, and a pair of transistors having different conductor characteristics, and the collectors of the transistors are directly connected to each other. Is connected to a capacitive load, and Includes anti, the emitter of said other transistor and a fourth amplifier comprising grounded via a capacitor, direct output of the first amplifier the fourth
Input to the base of one transistor of the amplifier, and the output taken out through the capacitor of the first amplifier is applied to the base of the other transistor of the third amplifier to directly connect the output of the second amplifier. Is input to the base of one transistor of the third amplifier, and the output taken out through the capacitor of the second amplifier is applied to the base of the other transistor of the fourth amplifier, so that the mutual outputs are Wide-band DC amplifiers configured as phase-balanced amplifiers.