SU453635A1 - Oscillographic sweep generator - Google Patents

Description

This invention relates to radio electronic devices and, in particular, can be used in wideband oscilloscopes. Oscilloscopic oscillator sweepers are known that contain a direct current amplifier (DCF), a time setting capacitor, a discharge transistor, a sweep control trigger, and a blocking capacitor. However, these generators have a large sawtooth delay time at start-up, to compensate for which delay lines are used in oscilloscopes. Lines with a longer delay have a narrow bandwidth, which limits the scope of use of the oscilloscope, longer recovery times, resulting in loss of information, for example, in personnel scans, as well as large dimensions, since a set of capacitors switched simultaneously is used to block from restarting with switching sweep durations. To reduce the generator recovery time and the start-up delay time and reduce the dimensions, the proposed generator is equipped with an operational amplifier and comparator, one input of which is connected to the output of the DC control, the other input to the common point of the power supply, and the output simultaneously through parallel-connected resistors and to the cathode of the diode, one input of the operational amplifier is connected to the output of the trigger, the other through a resistor to the output of the amplifier, and the output to the base of the discharge transistor. FIG. I shows a diagram of the proposed sweep generator; in fig. 2 - plots showing the operation of the scheme. The generator contains the DCF 1, the time setting capacitor 2, the discharge transistor 3, the trigger 4 of the sweep control, the comparator b, the operational amplifier 6. The time setting capacitor 2 is connected between the input and output of the DCA 1, the collector of the discharge transistor is connected to the input DCA 1, and its emitter through a resistor 7 is connected to a power source. The output of the trigger control trigger 4 is connected to the input 8 of the operational amplifier 6, the second input 9 of the operational amplifier 6 receives a signal from the output of the DC modulator I through the resistor 10 and through the resistor 11 from the comparator 5. The output of the operational amplifier 6 is connected to the base of the discharge transistor 3. The DCA 1 is connected through a resistor 12 with the trigger input 4 and the code 13 of the comparator 5. The second input 14 of the comparator 5 is connected to a common point of the power source. The signal from the output of the comparator 5 is fed through a resistor 15 to the cathode

diode 16. The anode of the diode 16 receives trigger pulses.

The scheme works as follows.

UFT 1 is covered by negative feedback, which includes an operational amplifier 6 and a discharge transistor 3, which ensures the stability of the UFD over current and, therefore, the stability of the initial level of the output voltage. In this case, the discharge transistor 3 is in a linear mode — and a small current flows through it. Trigger pulses arriving at point 17 transfer trigger 4. The voltage from the trigger output is fed to the input 8 of the operational amplifier 6, the output voltage from which goes to the base of transistor 3 and closes it. The linear charge of the capacitor 2 occurs, which corresponds to the formation of a forward stroke of the saw-tooth voltage. Threshold I „of comparator 5 is not much higher than the initial level. output voltage sweep generator.

When the output voltage reaches this threshold, the comparator 5 is triggered, but its effect on input 9 of amplifier 6 does not change the voltage of the latter, since the voltage at input 9 is less than the voltage on the input 8. When the sawtooth reaches its maximum value Ymax through the resistor 12, the trigger 4 returns to the initial state. At the same time, a potential change occurs at the output of the operational amplifier 6 due to the action of the voltage from the output of the nominal 5, and the transistor 3 opens. At this point, the formation of the reverse sawtooth voltage begins. When the sawtooth voltage reaches the threshold of the comparator 5, the feedback becomes valid negative, and the circuit returns to its original state.

The voltage received at the output of the comparator 5 is used to block the trigger input from restarting until the generator is fully restored.

Figure 2, and shows the trigger pulse sweep generator; on the plot of 2.6 - pulses generated by the trigger 4 and fed to the input 8 of the operational amplifier 6; plot 2, the pulses taken from the output of the comparator 5 and fed to the input 9 of the amplifier 6; On plot 2, d - the voltage supplied from the output of the operational amplifier 6 to the base of the transistor 3; on plot 2, d is the current of the comparator of transistor 3; plot 2, e - output sawtooth tension.

The initial current /,., The discharge current, the time of the driving capacitor / max in the proposed generator does not depend on each other.

Since in the initial state of the generator the discharge transistor is in a linear

In this mode, a small initial current (I) flows through it, and the turn-on time of transistor 3 is minimal and, accordingly, the delay is low but the sweep is started.

The subject invented

An oscilloscopic sweep generator containing an amplifier, a time setting capacitor, a discharge transistor, a diode, and a trigger, characterized in that

reducing the generator recovery time and the start-up delay time and reducing the size; it is equipped with an operational amplifier and comparator, one input of which is connected to the output of the amplifier, the other

the input is connected to the common point of the source, and the output is simultaneously connected via parallel-connected resistors to the input of the operational amplifier and to the cathode of the diode; one input operational amplifier connected to

the output of the trigger, another input through a resistor to the output of the amplifier, and the output to the base of the discharge transistor.

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