JPS6347666A - Oscilloscope - Google Patents

Abstract

PURPOSE:To prevent a leakage to a character amplifier and to make the display of a character or mark clear along with a wave form to be observed, by shortcircuiting a signal to be measured during a period displaying character. CONSTITUTION:When the output of a character/switching signal generator 40 is a high level, transistors 17, 18 are turned ON through a transistor 39 while transistors 15, 16 are turned OFF and a transistor 51 is turned ON and diodes 52, 53 are brought to a continuity state to shortcircuit the signals to be measured from input terminals 11, 12. Transistors 37, 38 are turned OFF and the output of a character amplifier 33 is applied to an output amplifier 14. Next, when the output of the signal generator 40 becomes a low level, no character signal is applied to the amplifier 14 and the signals to be measured are inputted to a main amplifier 13 to be applied to the amplifier 14. Therefore, the leakage between signals is prevented and switching is repeated to clearly display both signals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oscilloscope that displays characters such as letters and symbols on a screen simultaneously with signal waveforms.

As oscilloscopes become more sophisticated, characters such as letters and symbols representing measurement conditions and measurement data are increasingly displayed along with the measured waveform. The present invention
Specifically, the present invention provides an oscilloscope equipped with a circuit for enhancing the clarity of displayed characters and measured waveforms.

[Prior Art] A conventional circuit for displaying characters is shown in FIG. 4 and will be described.

Reference numerals 11 and 12 designate input terminals to which high-frequency signals to be displayed on a cathode ray tube (not shown) are applied as signals of opposite polarity from a previous stage amplifier (not shown). Resistors 21 and 22 are both load resistances of the preceding stage amplifier. 13 is a main amplifier, which amplifies the high frequency signals applied from terminals 11 and 12;
The signal is applied to the output amplifier 14 via transistors 15 and 16, amplified, and applied to the deflection plate of the cathode ray tube.

Here, the bases of transistors 15 and 16 are connected to common ground, and their bases are connected in common, and a bias voltage is applied by resistors 23 and 24.

Transistors 17 and 1 are connected between the emitters of transistors 15 and 16 to which the output of main amplifier 13 is connected.
The emitters of transistors 17 and 18 are connected together, and the collectors of transistors 17 and 18 are connected in common.

The bases of both transistors are also commonly connected to apply a character switching voltage.

Reference numerals 31 and 32 denote character signal terminals to which character signals from a character signal generator (not shown) are applied with opposite polarities. 33 is
This is a character amplifier for amplifying character signals applied to character signal terminals 31 and 32. The character signal amplified by the character amplifier 33 is applied to the input side of the output amplifier 14 via transistors 35 and 36 whose bases are connected to the ground.

The emitters of transistors 37 and 38 are connected between the emitters of transistors 35 and 36 whose bases are connected to the common ground, and the collectors of transistors 37 and 38 are connected in common. The bases of both transistors are also commonly connected, and a bias voltage is applied by resistors 41 and 42.

The bases of transistors 35 and 36 are connected in common, and also to the bases of transistors 17 and 18, and to the emitter of transistor 39, which forms an emitter follower with resistor 43.

A switching signal from a character switching signal generator 40 is applied to the base of the emitter follower transistor 39.

A timing signal from a character signal generator (not shown) is applied to this character switching signal generator, and a switching signal synchronized with this is applied.

The level of the switching signal applied to the base of the transistor 39 is either "H" or "L".

When it is "H", the base voltages of transistors 17 and 18 are higher than those of transistors 15 and 16, so transistors 15 and 16 are turned off, transistors 17 and 18 are turned on, and the main amplifier 13 The high frequency signal is not applied to the output amplifier 14. On the other hand, since the base voltages of transistors 35 and 36 become higher than those of transistors 37 and 38, transistors 37 and 38 are turned off, and collector current flows in transistors 35 and 36, making them active. , the character signal amplified by the character amplifier 33 is applied to the output amplifier 14, and the character is displayed on the cathode ray tube.

The output of the character switching signal generator 540 is “L”
When the power is on, the base voltages of transistors 35 and 36 are lower than the base voltages of transistors 37 and 38, so transistors 35 and 36 are turned off and transistors 37 and 38 are turned on, so that the voltage from the character amplifier 33 is No character signal is applied to output amplifier 14. On the other hand, since the base voltage of transistors 17 and 18 becomes lower than that of transistors 15 and 16, transistors 17 and 18 are turned off, and transistors 15 and 16 become active because collector current flows. , the high frequency signal amplified by the main amplifier 13 is sent to the output amplifier 14.
is applied, and the high-frequency signal waveform is displayed on the cathode ray tube.

In this way, various characters are displayed simultaneously with the display of a high frequency signal waveform including a high frequency component by being switched by a switching signal.

[Problems to be solved by the invention] The output of the character switching signal generator 40 is “H”.
In the OP mode, the character signal amplified by the character amplifier 33 is amplified by the output amplifier 14 via the active transistors 35 and 36, and the character is displayed on the cathode ray tube. At this time, the high frequency signal containing the high frequency component amplified by the main amplifier 13 must not be applied to the output amplifier 14 and must be completely blocked.

However, when the transistors 15 and 16 are off, the high frequency component of the high frequency signal leaks to the input side of the output amplifier 14 through the capacitance between the collector and emitter and other stray capacitances, and this becomes the character signal. There is a problem in that the characters, which are letters and symbols displayed on the CRT surface, become "blurred" and blurred.

Even if this leakage is small, it is enough voltage to thicken the thin lines that make up the character and make them look "blurred."

This "blur" appears more prominently the higher the frequency component of the high-frequency signal and the broader the output of the main amplifier 13, making it difficult to read the characters. It contained major problems.

Similarly, when the measured waveform is displayed, high frequency components of the character signal are transmitted to the output amplifier 14 through the collector-emitter capacitance when transistors 35 and 36 are off and other stray capacitances. The major problem was that this leaked to the input side of the monitor and was superimposed on the signal under test, causing the waveform under test displayed on the CRT to become "blurred" or distorted.

[Means for Solving the Problems] The present invention has been made to solve these problems. Recognizing that there are stray capacitances in circuits such as the Each of them is reduced by the period during which the measured waveform is displayed.

[Function] The character switching signal turns on and off a switch provided between the input terminals of the main amplifier 13 or the character amplifier 33, so that a high frequency signal or a character signal containing high frequency components is sent to the main amplifier 1.
3 or the character amplifier 33 so as not to be amplified.

As a result, even if a high-frequency signal with a width of approximately It is now possible to eliminate leakage due to electrostatic capacitance, etc. This eliminates "poke" and waveform distortion in characters and measured waveforms, making it possible to display even complex characters and measured waveforms extremely clearly.

Examples] An embodiment of the present invention will be described with reference to FIG.

Here, elements corresponding to each element of the circuit shown in FIG. 4 are given the same numbers.

Reference numerals 11 and 12 are input terminals to which high-frequency signals to be displayed on a cathode ray tube (not shown) are applied as signals of opposite polarity from a previous stage amplifier (not shown). Resistors 21 and 22 are both load resistances of the preceding stage amplifier. Diodes 52 and 53 are connected in parallel with these load resistors 21 and 22. 13 is the main amplifier, and terminals 11 and 12
Transistor 15 amplifies the high frequency signal applied from
and 16 to the output amplifier 14, where it is amplified and applied to the deflection plate of the cathode ray tube.

Here, the bases of transistors 15 and 16 are connected to common ground, and their bases are connected in common, and a bias voltage is applied by resistors 23 and 24.

Transistors 17 and 1 are connected between the emitters of transistors 15 and 16 to which the output of main amplifier 13 is connected.
The emitters of transistors 17 and 18 are connected together, and the collectors of transistors 17 and 18 are connected in common. The bases of both transistors are also commonly connected, and the character
A switching voltage is applied.

Reference numerals 31 and 32 denote character signal terminals to which character signals from a character signal generator (not shown) are applied with opposite polarities. 33 is
This is a character amplifier for amplifying the character signal applied to the character signal @terminals 31 and 32. The character signal amplified by the character amplifier 33 is applied to the input side of the output amplifier 14 via transistors 35 and 36 whose bases are connected to the ground.

The emitters of transistors 37 and 38 are connected between the emitters of transistors 35 and 36 whose bases are connected to the common ground, and the collectors of transistors 37 and 38 are connected in common. The bases of both transistors are also commonly connected, and a bias voltage is applied by resistors 41 and 42.

The bases of transistors 35 and 36 are connected in common, and also to the bases of transistors 17 and 18, and to the emitter of transistor 39, which forms an emitter follower with resistor 43. A switching signal from a character switching signal generator 40 is applied to the bases of the three transistors forming the emitter follower. A timing signal from a character signal generator (not shown) is applied to this character switching signal generator, and a switching signal synchronized with this is applied.

The switching signals of the emitters of the three transistors are divided between a resistor 56 and a resistor 57 connected in parallel with a capacitor 58, and are applied to the base of the transistor 51. The transistor 51 has its emitter connected to ground,
The emitter voltage of the transistor 51 is provided by the constant voltage diode 55 . The switching signal turns transistor 51 on and off, and when on, conducts current from diodes 52 and 53, whose collectors are connected, thereby creating a short circuit between input terminals 11 and 12, causing the main Prevent high frequency signals from being applied to the amplifier 13. When the transistor 51 is off, no current flows through the diodes 52 and 53, and the signals applied to the input terminals 11 and 12 have opposite polarities. is off and has no effect.

The level of the switching signal applied to the base of the transistor 39 is "H99" or "H99".

''Hpp, the base voltages of transistors 17 and 18 are higher than those of transistors 15 and 16.
is off, transistors 17 and 18 are on,
The high frequency signal from main amplifier 13 is not applied to output amplifier 14.

Furthermore, when the level of the switching signal is "Het", since the transistor 51 is turned on, current flows through the diodes 52 and 53, turning them both on, thereby preventing the high frequency signal from being applied to the main amplifier 13. , leakage of high-frequency signals to the output amplifier 14 due to capacitance between the emitters and collectors of transistors 15 and 16 that are turned off is prevented. It is extremely effective when applied to terminals 11 and 12.

On the other hand, when the switching signal level is "H",
Since the base voltages of transistors 35 and 36 are higher than those of transistors 37 and 38, transistors 37 and 38 are turned off, and transistors 35 and 36 become active with collector current flowing, so the character The character signal amplified by the amplifier 33 is applied to the output amplifier 14, where it is amplified without being affected by the high frequency signal, and a clear character is displayed on the cathode ray tube.

The output of the character switching signal generator 40 is “L”
'', the base voltages of transistors 35 and 36 are lower than the base voltages of transistors 37 and 38, so transistors 35 and 36 are turned off, transistors 37 and 38 are turned on, and the voltage from the character amplifier 33 is No character signal is applied to output amplifier 14.

On the other hand, the transistor 51 is turned off and the diode 52
and 53 are also turned off, so input terminals 11 and 12
The high frequency signal applied to the main amplifier 13 is directly applied to the main amplifier 13. At the same time, transistors 17 and 18
Since the base voltage of transistors 15 and 16 is lower than that of transistors 17 and 1
8 is turned off, and collector current flows through transistors 15 and 16, making them active. The high-frequency signal amplified by the main amplifier 13 is applied to the output amplifier 14, and the high-frequency signal waveform is displayed on the cathode ray tube. be done.

In this way, various characters are displayed extremely clearly at the same time as the high frequency signal waveform containing high frequency components is displayed by being switched by the switching signal.

Another embodiment of the invention is shown in FIG. Here, the same numbers and symbols are used for components corresponding to FIGS. 1 and 4.

In FIG. 2, the difference from the conventional example shown in FIG.
The anodes of diodes 45 and 46 are connected between 1 and 32, the cards are connected in common, and this is connected to the emitter of transistor 39.

As a result, the level of the switching signal becomes “L 91
When , transistors 17.18 and 35.36
is turned off, collector current flows through transistors 15 and 16, and transistors 37.3 and 16 become active.
8 is turned on, the high frequency signal amplified by the main amplifier 13 is amplified without being influenced by the character signal, and a clear waveform is displayed on the cathode ray tube.

FIG. 3 is a combination of the circuits shown in FIGS. 1 and 2, and as is clear from what has already been explained,
Since it has the characteristics of the circuit shown in FIG. 1 and the characteristics of the circuit shown in FIG. 2, it is possible to display clear signal waveforms and clear characters.

In the above description, a case has been exemplified in which a signal sum 1q reduction means using diodes 52 and 53 is inserted between input terminals 11 and 12 and main amplifier 13. However, such signal gain attenuation means may be provided inside the main amplifier 13 and may also be provided at the input terminals 11 and 12.
It will be obvious that it may be provided in a pre-amplifier (preamplifier) for supplying an input signal to the input signal.

Similarly, it will be obvious that the character signal gain reduction means by diodes 45 and 46 may also be provided inside the character amplifier 33, other than as shown in FIG.

Transistors 15, 16 (35, 36> and 17.
18 (37, 38) is an observation signal disconnection means (character signal disconnection means) for connecting or disconnecting the signal to be observed (character signal) to the output amplifier 14.
1 to 3, and the signal gain reduction means only needs to act on this observation signal disconnection means (character signal disconnection means) so that a large high frequency signal is not applied at the time of disconnection. The diode (52, 5
3, 45, 46>, it will be clear from the above description that it may be configured by a transistor or a field effect transistor.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, even when observing a large amplitude signal rich in high frequency components, characters and symbols can be clearly displayed on the CRT surface. In addition, it is possible to display clear signal waveforms without being affected by character signals at a low cost, and by making oscilloscopes more intelligent,
The effects of the present invention are extremely significant in a situation where the number of displayed characters increases and becomes more complex, and furthermore, as the frequency band becomes higher, it is necessary to observe higher frequency signals.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram showing another embodiment of the invention, and Fig. 3 is a circuit diagram showing yet another embodiment of the invention. FIG. 4 is a circuit diagram showing a conventional example. 11.12... Input terminal 13... Main amplifier 14
...Output amplifiers 15-18...Transistors 21-24...Resistors 31, 32...Character signal terminal 33...Character amplifiers 35-39...Transistor 40...Character switching signal generation Vessel 41~
43...Resistance 45.46...Diode 51.
... Transistor 52.53 ... Diode 55 ... Constant voltage diode 56.57 ... Resistor 5
8... Capacitor.

Claims (5)

[Claims] (1) Signal amplification means for amplifying the signal to be observed, observation signal disconnection means for connecting and cutting off the output of the signal amplification means, and character amplification for amplifying the character signal to be displayed. means for connecting and cutting off the output of the character amplifying means; and when the observation signal cutting and cutting means is in the connected state, the character signal cutting and cutting means is cut off and the observation signal is cut off. Character switching control means for controlling the character signal disconnection means to be in the connected state when the signal disconnection means is in the disconnected state; the observation signal disconnection means in the connected state; and the observation signal disconnection means in the connected state. In an oscilloscope, the oscilloscope is equipped with a character signal disconnection means, and an output means for applying the output to a cathode ray tube, wherein at least one of the signal amplification means and the character amplification means outputs the amplified signal. An oscilloscope comprising: signal gain attenuation means for attenuating the gain when no signal is applied to the oscilloscope. (2) The signal amplification means includes a main amplifier and a preamplifier connected upstream of the main amplifier, and the gain reduction means is provided between the preamplifier and the main amplifier. An oscilloscope according to claim 1. (3) The oscilloscope according to claim 1, wherein the character amplification means is provided with the gain reduction means at its input terminal. (4) The gain reduction means is constituted by a diode for short-circuiting the output of the preamplifier, and the output of the first preamplifier is short-circuited by flowing current through the diode. Oscilloscope as described in section. (5) The gain reduction means is constituted by a diode for short-circuiting the input terminal of the character amplification means, and the input terminal of the character amplification means is short-circuited by passing a current through the diode. The oscilloscope described in scope 3.