US2605403A - Multivibrator circuit - Google Patents

Description

WITNESSES: 5% W2 9%. f w I July 29, 1952 Filed Au 12, 1950 WZ'L 1m 35 i l;

INVENTOR Lawrence H.Crondon.

Patented July 29, 1952 MULTIIVIBRATORI 'omom'r Lawrence ILCi-andon, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, P a., a corporation of Pennsylvania Application August 12, 1950, Serial No. 179,057

My invention relates to electrical apparatus and particularly to electronic circuitsof the multivibrator type.

Many electronic systems require a. source of sharp pulses of short time duration, and having an essentially square wave form. A number of multivibrator circuits which exist in the prior art of which I am aware, attempt to produce such pulses. These circuits, however, leave much to bedesired in the wave form and amplitude of the output pulse.

It is,'accordingly, a broad object of my invention to provide an improved multivibrator circuit.

It is another object of my invention to provide a multivibrator circuit which will produce voltage pulses of short time duration having steep rise and decay characteristics, and having an amplitude substantially equal to that of the supply voltage.

In accordance, with my invention, I provide a multivibrator circuit comprising a pair of electronic tubes, one of which. may be a triode and the other a pentode. The circuit of my invention is arranged so as to provide feedback from the triode, to the cathode, and the screen and suppressor grids of the pentode, whereby voltage pulses having desirable characteristics including very short rise and decay times and relatively large amplitude are provided.

Other objects and advantages of my invention will appear from the following description of a preferred embodiment, taken in connection with the accompanying drawing, in which the single figure is a schematic diagram of a preferred embodiment of my invention.

The multivibrator circuit shown in the draw-- ing includes a pair ofelectronic tubes, one of which may be a triode I I and the other a pentode I3. The cathodes I5, II of these tubes are connected through a common bias resistor III to ground 2|. The positive terminal 23 of a direct current anode potential source (not shown) is connected through a. first resistor 25 to the anode 21 of the pentode I3, and through second and third resistors 29, 3| to the anode 33 of the triode II. The anode 21 of the pentode I3 is connected through a capacitor 35 to the control grid 31 of the triode II. A fourth resistor 39 is connected between the control grid 31 and cathode I5 0! the triode II. The screen grid M of the pentode I3 is connected to the anode 33 of the triode II. The control and suppressor; grids 43, 45 of the pentode I3 are connected to ground 2 I. A by-pass capacitor 41 is connected from the 'junction of the second and third resistors 29, 3|

;7 claims. (01. 250-27) -1 2 to ground 2|. application of trigger pulses between the control grid 31 of the triode II and ground 2I. pulses are taken from terminals 5| provided between the anode 21 of the pentode I3 and ground 2|.

In the operation of the circuit, the triode II is normally conductive and the pentode I3 is normally non-conductive. To get an output pulse, a negative trigger pulse is applied to the grid 31 of the triode II. This reduces the plate current of the triode II, which in turn decreases the voltage drop across the cathode bias resistor I9. Reduction in voltage drop across thecathode bias resistor I9 makes the pentode control and suppressor grids 43, 45more positive with respect to the cathode I'I. At the same time the plate voltage on the triode II has increased which has theeffect of making the pentode screen grid.

4| more positive with respectto the cathode I]. As a result of these effects which operate simultaneously, the pentode I3 becomes suddenlyconductive. The anode voltage of the pentode I3 is lowered, making the control grid 31 of the triode I I more negative. This action is cumulative until the triode II is cut ofi and the pentode I3 is fully conductive. The coupling capacitor 35 then begins to charge through the fourth resistor 39 making the control grid 31 of the triode II more positive. This action continues until the cut-oif J point is reached, at which time the triode II again conducts. Current through the triode will then increase the voltage drop across the cathode bias resistor I9 which will tend to make the pentode control andpsuppressor grids 43, 45 more negative. At the same time, the plate voltage-on the'triode I I has decreased, which has the effect of making the pentode screen grid 4I more negative with respect to the cathode II. These effects are cumulative until the pentode I3 is cut of! and the triode II is again fully conductive.

In the practice of my invention I have used the following circuit constants with good results: pentode tube I3, type 6AG7; triode tube II, type 12AU7 (sections connected in parallel); first resistor 25, 22,000 ohms; second resistor 29, 6,200 ohms; third resistor 3|, 2,800 ohms; fourth resistor 33, 100,000 ohms; cathode bias resistor I9, 500 ohms; coupling capacitor 35, 4 to 30 micromicrofarads; by-pass capacitor 41, 0.5 microi'arad.

I am aware that some modifications of the circuit shown and described could be made without departing from the scope of my invention. I desire, therefore, to be limited only insofar Terminals 43 are provided for".

Outp t as is necessitated by the prior art and the spirit of the appended claims.

I claim as my invention:

1.'A multivibrator circuit comprising a first electronic tube having an anode, a cathode, and a control grid, a second electronic tube having an anode, a cathode, a control grid, a screen grid, and asu pressor-grid, abias'resistor connected between said cathodes and ground, meansconnected to supply anode potential to said tubes,

means coupling the anode of said second tube 1 to the control grid of said first tube, a connection from the anode of said first tube to the screen grid of said second tube, and connectionsirom l the suppressor and control grid of said s'econd tube to ground. r

2. A multivibrator circuit comprisinga first; electronic tube having an anode, a cathode, and

a control grid, a second electronic tube having i an anode, a cathode, a-lcontrol grid, a screen grid, and a suppressor grid, a bias resistor, con-.

nected between: said cathodes sand, ground-,- means connectedto supply'anode potential to said tubes, means coupling theranode: of said second ,tube to the control grid of said firsttube aconnection from the anode of said first tube to the; screen grid of said second ltd-be, connections from the suppressor and controhgridofrsaid second tube-to ground, landimeans to apply .atrjigger pulse-to; th

' control electrodeofsaidrfirsttuhe.

35A "multivibra'tor: circuit. comprising a first normallyconductiv'e electronic tube havingwzan.

anode, a: cathode and a; control, 1 electrode, a second normally non-conductive electronic tube having' an anode, l aLcath'ode, control, screen, and suppressor 'grids, rneanscconnected. xtojsupply direct current anode potential to: said'itubes, con-.- duc'tors" connecting saidz cathodes together and through a bias resistor ito ground, ymeanscou:

pling the anode of said;v second-tube to ;the.;ccn:- trol-grid of said first tub'e; means connecting, the anode --of said first tube-to the :screen-;grid' of said second tube, conductors connecting ythe' control grid and suppressor grid of said ,second tube "to ground, and means for applying :a.:-nega@-. tive trigger--pulse 'to the lcontrol grid; "of said.

first-tube 1 V 4. multivibratorcircuitcomprising; .a first.

normally conductive electronic tube having: "an' anode, =a 'cath'ode', and a control electrode, :aisecond normally non conductive electronic" tube; havingamanede a cathode, control, screen, .and

suppressorgrids meansconnected to. supply direct" current "anode potential to said tubes,:- conductors 'connecting said cathodes together and through -a bias resistor'to-g round', means-include ing a'f capacitor for coupling the anode oil-said,

ond normally non-conductive electronic tube having an anode, a cathode, control, screen, and

"suppressor" grids, means connected to supply di- "rectcurrerit anode potential to said tubes, conductors-connecting saidcathodes together and th-rough' -a bias'resistor to ground, a capacitor connected between the anode of said second tube and the control grid of said first tube, and a resis'tor connected between the control grid and cathode of said first tube, means connecting the anode of saidifirst tube to the screen. rids-of said-seccndstube, c nd ctors; wnnectingthacontrol grid and suppressor grid of said second. tube,

to ground, and means ior applyi a negative tri serzpul e to thecontrolgr-idof said first tube 6.A' multivibrator circuit, comprising a first electronic tube having an anod a cathode; and a controlgrid, .asecond electronic tubeihaving.

an anode, a cathode, 'control,1,.v screen, and suppressor grids, a common-cathode bias resistor, and coupling means connected toiprovide ieed back voltage from said-;first=:.tube to the control,

screen; andisupnressorsgrids 'of; said second-:tube-..

7;.A multivibrator 'circuihcomprising. a first electronic tube having :an anode, a cathodeyand a 7 control grid, 11a se,cond,-:,electronic .tube having. an anode, ,ia. cathode,: a icontrol grid, a' -screen. grid, and agsuppressor ;grid,;.a-bias: resiston; means for connecting said cathodes through. said-biasg resistorto a point :of: reference potential,:mea'ns coupling the anode of .said; second :tube to; thev control grid f said :fir'stn tube; means ..'coupling: theq'anode ofsaid first tube to theescreeni-grid; of.isaid secondmube, and ;means coupling-the control and suppressor: grids of saidsecondztubeand; the controli-gridvofcsaidifirst tube to i-saidpoint ofpreferencezpotential. 1 .1

LAWRENCE-H.- oRANDoNf I]REFEnENcEs.-jc1frED The f'ollowing references are of fileof" this patent: 7

UNITEDLSTATESTPATENTS Number, 7 .Name Date 2,330,638: :Stratton inn-ri sseptlaasaiega record in the

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