US2456700A - Device adapted to produce sawtooth oscillations - Google Patents

Description

Dec. 21, 1948-. I J. HAANTJES 2,456,700

DEVICE ADAPTED TO PRODUCE SAW TOOTH OSCILLATIONS Filed April 24, 1946 FIG.2

VOLTAGE INVENTOR JOHAN HAANTJES ALI'TORNEY.

Patented Dec. 21, 1948 OFFICE 2;45.Ii,700 IiEVICEADAPIED T PRODUCE S'AW- TOOTHUSCIIJLATIONS .Iohanr Beauties}. Eindhoven, Netherlands, as=- Signor,-

by." mes-net assignments, to Hartford.

National Bank- -and- Trust Company, Hartford,

Conn, as trustee Applfc'atien April 24, 1946;: Serial No. 664,499 ln the Netherlands November 20, 1942 section 1; Public Law 690-; August s; 1946 Patent'expires November 20, 1962' 1.. This invention relates to a device adapted to produce saw-tooth oscillations} comprising acondenser-which is charged through a resistance and which maybe discharged through a gasfilled discharge tube havinga" control" electrode; In a circuit of' thistype it i's conventional"- to include a resistance capacitance parallel network between the cathodepfthe discharge-tubeand one end of the charged condenser; the other end thereof beingconnect-e to'tlre 'anodeof 'the tube. This network serves -to shorten'theextinction period" of" the time. one known circuitor this type is shown*schematically in Fig: l ofth'e drawing wherein a condenser I is connected via a resistance 2'- to a source-of cha rgirrg potential 3. Also provided is a gaseous-discharge tube 4" whose anode is connected to the jiiiictibri of resistance 2 and condenser I, and whose'cath'od is connected in "serieswith a condenser 5 to said other end of condenser I, condenser 5 being shunted by a resistaneeti- Thecontrol grid of tube 4 is connected through a resistance 1 to the end of condenser 5 which is remote from the cathode so that the voltage established across the parallel network constituted by resistance 6 and condenser 5 is impressed on the control grid. In the circuit described condenser 5 is charged to a high voltage during the discharge of condenser I through tube 4. This results in the grid of tube acquiring a negative voltage relative to the cathode, due to which in cooperation with the decreasing anode voltage tube 4 is blocked. During the subsequent period of charge of condenser I, condenser 5 is slowly discharged through resistance 6 until the negative voltage set up at the grid has attained the voltage required at the grid for the ignition of tube 4. Since the end of the period of charge of condenser I is substantially determined by the negative grid-bias set up across condenser 5, the frequency of the oscillations produced is dependent on the value of resistance 6 and of condenser 5. The circuit described offers the advantage that at the beginning of the period of charge of condenser a high negative voltage is set up at the grid of tube 4. By this voltage the positive ions present in the tube are carried off, due to which the period of extinction of tube 4 is very short and the deformation of the saw-tooth voltage across condenser I at the beginning of the period of charge, which deformation occurs with a lon period of extinction, is avoided.

This is offset, however, by the drawback that for the synchronization of the circuit concerned by means of a synchronization signal whose frequency is considerably higher than the natural frequency, a comparatively high synchronization voltage must be supplied to the gridof' tube 4 According tothe invention, this drawback'is obviated by including two series-connected' con densers in the cathode lead of the discharge tube, each oi'which is shunted by a resistance, the period'of discharge of one condenser being smaller and that of the other condenser being: considerably greater than the period of oscillation of the oscillations to be produced.

One form of construction of a circuit accord ing to the invention is shown, by way of example, in Figure 2 of the drawing.

In this circuit the cathode lead includes. two series-connected condensers 8 and. 9 shuntedlre spectively by resistances I6 and II.-

In Fig. 3 the variation of the negative voltage set up at the grid of tube 4 in the -circuit'ishown in Figure 1 during the period'of charge' of' condenser I is represented by curve a. The voltage requiredat the grid for the ignition of tube v 4 as a function of the anode voltage appearing during the said period of charge is represented by curve I). In the point of intersection of curves at and 1) tube 4 is ignited without a syn.- chronization voltage being required for the purpose. However, before the grid voltage of tube 4 has reached the said point of intersection, the negative grid-bias at any moment can be reduced to the ignition. voltage required at this moment by means of a positive synchronization voltage supplied to the grid. As appears from the figure, the required synchronization voltage, which at any moment is determined by the difference of the voltages represented by curves a and b, rapidly increases, according as the fre quency of the synchronization voltage more deviates from the natural frequency of the sawtooth generator.

In the circuit according to the invention the period of discharge of condenser 8 is smaller than the period of oscillation of the oscillations to be produced, due to which during the period of charge of condenser I condenser 8 is rapidly discharged and during the remaining part of the period of charge of the condenser the negative voltage at the grid is solely determined by the voltage set up across condenser 9. The period of discharge of condenser 9, however, is considerably greater than the period of oscillation of the oscillations to be produced, so that the voltage set up across condenser 9 during the period of charge of condenser I decreases but slightly. The variation of the resulting voltage at the grid of tube 4 as a function of time is represented by curve c in Figure 3, the voltage set up at the beginning of the period of charge being determined by the discharge curve of condenser 8 and the voltage set up during the remaining part of the period of charge by the discharge curve of condenser 9. As it appears from the variation of curve 0, the positive synchronization voltage required, which is determined by the difference of the voltages represented by curves and b, is at any moment considerably smaller than in the circuit shown in Figure 1. At the beginning of the period of charge, however, the voltage at the grid is as high as in the known circuit, so that the advantage of this circuit is retained.

The circuit according to the invention thus permits of obtaining a device for producing sawtooth oscillations, which is capable of being controlled by low synchronization voltages over a wide frequency range.

What I claim is: l

1. An arrangement for generating sawtooth oscillations having a predetermined periodicity, said arrangement comprising a condenser, a resistor, a source of constant potential connected across said condenser through said resistor, a gaseous discharge device having a control electrode, a first resistance-capacitance parallel network, a second resistance-capacitance parallel network, said device being connected in series with said first and second networks across said condenser, the discharge period of said first network being smaller than and the discharge period of said second network being greater than the oscillation period of the sawtooth oscillations to be generated, and means to apply the voltage developed across the series-connected first and second networks to said control electrode.

2. An arrangement for generating sawtooth oscillations having a predetermined periodicity, said arrangement comprising a, capacitative element, a resistive element, a source of constant potential 4 for chargin said capacitative element and connected thereacross through said resistive element, a gaseous discharge device having a cathode, a control electrode'and an anode, a first resistancecapacitance parallel network, a second resistancecapacitance parallel network, said anode being connected to one end of said capacitative element 'and said cathode being connected in series with said first and second networks to the other end 'of said capacitativeelement, the discharge period of said first network being smaller than and the discharge period of said second network being greater than the oscillation period of the sawtooth oscillations to be generated, and a resistor connected between said control electrode and said other end of said capacitative element.

3. An arrangement for generating sawtooth oscillations having a predetermined periodicity, said arrangement comprising a capacitative element, a resistive element, a source of constant potential for charging said capacitative element and connected thereacross through said resistive element, a gaseous discharge device having a cathode, a control electrode and an anode, a first resistancecapacitance parallel network, a second resistancecapacitance parallel network, said anode being connected to one end of said capacitative element and said cathodebeing connected in series with said first and second networks to the other end of said capacitative element, the discharge period of said first network being smaller than and the discharge period of said second network being greaterthan the oscillation period of the sawtooth oscillations to be generated, a resistor connected between said control electrode and said other end of said capacitative element, and means to impress synchronizing pulses to said control electrode. 1

. J OHAN HAANTJ ES.

, No references cited.

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