US3428902A

US3428902A - Monostable wide range multivibrator

Info

Publication number: US3428902A
Application number: US505435A
Authority: US
Inventors: Alexander A Gorski
Original assignee: United States Department of the Army
Current assignee: United States Department of the Army
Priority date: 1965-10-27
Filing date: 1965-10-27
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18

Description

Feb. 1s, 1969 Alexander A. Gorski,-

INVENTOR www Mew United States Patent O 3 Claims ABSTRACT OF THE DISCLOSURE A Wide range vacuum tube monostable multivibrator that has the ability to be retriggered ba-ck to the stable condition before the normal cycle of regenerative action occurs through the regular time constants. The normally conducting tube is adapted to receive a positive pulse at its cathode for triggering the normally conducting tube off. The two tubes of the monostable multivibrator are triodes and are Wired with a parallel resistor-capacitor circuit connected from the plate of the normally conducting tube to the grid of the normally nonconducting tube. The grid of the normally nonconducting 'tube is connected through a resistor to a negative voltage source. The cathode of the normally nonconducting tube is connected directly to ground. The cathode of the normally conducting tube is connected to the positive pulse source and further on to ground through a resistor. Both plates are connected to a positive voltage source through separate voltage dropping resistors. A capacitor is connected between the plate of the normally nonconducting tube to the grid of the normally conducting tube.

A third triode vacuum tube used as a cathode follower is included in the wide range monostable multivibrator circuit with its plate connected `directly to the positive voltage sour-ce to which the plates of the other triodes are connected. The cathode of the third triode is connected to the grid of the normally conducting tube and to the cathode of a grid catcher diode. The anode of the grid catcher diode is connected back to the grid of the cathode follower triode through a voltage divider that has a negative voltage applied to both the anode of the grid catcher and to the grid of the cathode follower, thus, insuring cut off of the cathode follower and a negative voltage limiter at the grid of the normally conducting tube of the monostable multivibrator. The cathode follower is adapted to receive a positive pulse at its grid for causing conduction thereof. When the cathode follower conducts, the positive voltage source is applied to the grid of the normally conducting tube for retriggering conduction at any time during which the tube is not conducting.

This invention relates to an improved monostable multivibrator and more particularly to a monostable multivibrator circuit that has the ability to be retriggered, along a negative voltage plateau limited by a clipper circuit, back to the stable condition at a time before the normal cycle of regenerative action occurs.

Monostable multivibrator circuits are Well known in the art. A multivibrator is a circuit generally consisting of a pair of electron tubes cross coupled in such a manner that one of the tubes conducts at a given instant while the other is in a nonconducting condition. In the stable condition of the monostable multivibrator, the circuit is arranged to prefer conduction of one of the electron tubes over the other, and, left undisturbed, will always be in a condition wherein a first tube is conducting and a second tube is nonconducting. An input pulse will cause a quasistable condition resulting in a negative pulse or gate of a particular length of time coming from the plate of the 3,428,902 Patented Feb. 18, 1969 ice normally nonconducting tube. Conventionally, transient time of the quasi-stable condition is determined by applied voltages and the basic circuit elements. In this invention a means is available for returning the circuit back to a stable condition at a time less than would be the case employing conventional means.

The purpose of the monostable wide range multivi- Ibrator is to control a suppressor voltage in order to provide a wide range gate for a 4.5 mega-cycle amplifier. The required range is for a 40 lusec. to 1000 aseo. gate, however, the circuit has been operated over the l0 lasec. to 10,000 asec. range.

In accordance with the invention, a monostable multivibrator circuit is provided with means for triggering its state from a normally stable condition to a quasi-stable condition. The multivibrator circuit is also provided with a cathode follower type device which is normally cut oif and has .an input source to its grid and has its cathode connected to the grid of the normally conducting multivibrator stage. By means of a positive pulse, the cathode follower conducts ending the quasi-stable condition in the multivibrator. The anode of the cathode follower is returned to a positive voltage source such that when the cathode follower conducts, a low impedance path from the positive voltage source is established to the grid of the normally conducting multivibrator stage. This circuit permits the quasi-stable state of the multivibrator to be terminated, thus, ending the circuits output pulse substantially instantaneously.

It is accordingly an object of this invention to provide a Wide range gate for an amplilier.

Itis another object of this invention to provide an accurate means for terminating the unstable state of the monostable multivibrator.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein the single figure is a schematic diagram of one embodiment of the invention.

Referring now to FIGURE 1, a monostable multivibrator is composed of

electron tubes

10 and 12, each having an anode, a grid and a cathode denoted by 14 and 16, 18 and 20, and 22 and 24, respectively. Anode 14 is connected to a source of a positive voltage through plate load resistor 26. Anode 16 is also connected to the positive voltage source through plate load resistor 28. Cathode 22 of tube 10 is connected to ground through resistor 30, while cathode 24 of tube 12 is connected directly to ground. The grid 20 of tube 12 is connected to both a negative voltage source through resistor 32 and to anode 14 of tube 10 through an RC parallel combination consisting of resistor 34 and capacitor 36. Timing capacitor 38, which determines the normal regenerative time of the unstable state of the multivibrator, is inserted between anode 16 of electron tube 12 and grid 18 of electron tube 10.

A third electron tube 40 with anode 42, grid 44 and cathode 46, which is normally cut olf, can be made to conduct with a normal amplitude pulse injected to grid 44 from terminal 50 through capacitor 48. Anode 42 is connected to a source of positive voltage. A 'voltage divider comprising resistor 52, resistor 54, with resistor 56 and capacitor 58 connected in parallel, all serially connected between a negative voltage and ground. 'Ihe grid 44 of electron tube 40 is connected to the juncture ibetween resistor 52 and resistor 54 of the voltage divider through resist-or 60. A diode 62 wtih anode 64 and cathode 66 is used as a clipper circuit. An-ode 64 is connected to .the juncture between resistor 54 and the parallel combination of resistor 56 and capacitor 58. Cathode 66 is connected to both grid 18 of electron tube 10 and cathode 46 of electron tube 40. The voltage applied to anode 64 is set at a predetermined negative level and provides a conducting path to ground when voltage on cathode 66 becomes a negative value with respect to the anode 64. It can be seen that diode 62 acts as a grid catcher when the voltage on grid 18 goes more negative than the voltage level at anode 64.

The monostable multivibrator portion of the circuit diagram is conventional and its operation will be set out only in brief. Resistor 32 and resistor 34 values, along with the value of the potential source lapplied to one side of resistor 32, are chosen to secure normal conduction in electron tube and normal nonconduction in electron tube .12. A positive trigger pulse applied at terminal 70 is coupled to cathode 22 through capacitor 68. Due to this sudden back biasing of tube 10, it will cease conduction. The potential at anode 14 will rise immediately to a positive maximum coupling this positive voltage to grid 20 of tube 12 through capacitor 36 causing conduction of tube 12. Voltage at anode 16 drops abruptly and is further coupled to grid 18 through capacitor 38. It is desired that in the operation of the two tubes that electron tube 12 will conduct for only a brief period wit-h tube 10 cut off. Normally, regenerative action would take a period of time corresponding to the R'C time constant product of resistor 28 and capacitor 38. However, in this circuit tube 10 is caused to resume conduction at a time sooner than would be the case in normal regenerative action.

The undisturbed period of time that the circuit will maintain itself in the unstable state, with tube 12 conducting and tube 10 cut off, is determined by how long grid 18 is maintained below cut off voltage. The diode clipper holds grid 18-to a proper negative potential with the remaining negative voltage being dropped across the diode itself. A positive voltage applied at terminal 50 is coupled to grid 44 of electron tube 40 through capacitor 48. This positive voltage pulse will cause tube 40 t-o conduct. With tube 40 conducting, it furnis-hes a low impedance path from the positive source through grid 18, cathi ode 22 and on to ground. With this sudden rise of Voltage on grid .18, tube 10 starts conducting thereby accurately terminating the output pulse of the multivibrator. A positive voltage pulse applied at terminal 70 can start the cycling process over again.

The present invention is applicable when a gate circuit needs to be operated at a higher frequency than the normal restoring time constants of the circuit. If no gate ending pulses are applied, the circuit will operate as a normal monostable multivibrator generating a gate determined by R-C time constant in the grid circuit of tube 10.

Obviously, many ymodifications and variations of the present invention ,are possible in the light .of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A wide range monostable multivibrator comprising first and second electron tubes, said first electron tube having a current fiow path and first and second current fiow regulating elements, said first current flow regulating element being a cathode of said first electron tube, and said second electron tube having a current flow path and a current fiow regulating element, said first electron tube being biased to a normally conducting state, and said second electron tube being biased to a normally nonconducting state, means for applying a trigger pulse to said cathode of said first electron tube for shifting states of said monostable multivibrator; a time constant circuit directly coupled from the current flow path of said first electron tube to said current fiow regulating element of said second electron tube; a third electron tube normally 4 in a cutoff condition having as its load said second current iiow regulating element of said first electron tube, means for causing conduction in said third electron tube to impart conduction instantaneously in said first electron tube when said first electron tube is in its quasistable state; and a voltage limiting means for limiting the negative `voltage on said second current flow regulating element of said first electron tube when said first electron tube is in its quasistable state of nonconduction, thereby decreasing the time required for said first electron tube to resume conduction.

2. A wide range monostable `multivibrator comprising a first electron tube having an anode, a grid and a cathode; a second electron tube having .an anode, a grid and a cathode; means connecting said cathode to ground potential, a positive potential source connected through a resistor to the anodes lof both said first and second electron tubes; a resistor and a capacitor connected in parallel between the anode of said first electron tube and the grid of said second electron tube and further connected to a negative potential source through a resistor; a capacitor connected between the anode of said second electron tube and the grid of said first electron tube; a third electron tube having an anode, a grid and a cathode, said anode being connected to said positive potential source, and having as its load the grid circuit of said first electron tube; means for applying an on trigger pulse to the grid of said first electron tube, a diode clipper with an anode and a cathode, said anode connected to the grid of said third electron tube and said cathode connected to grid of said first electron tube; a negative voltage divider source connected to the anode of said diode for back biasing the diode to a desired negative voltage, said negative voltage divider further connected to the grid of said third electron tube and means for applying an off trigger pulse to the grid of said third electron tube.

3. A wide range monostable multivibrator comprising a first electron tube having an anode, a grid and a cathode, a second electron tube having an anode, a grid and a cathode, means connecting said cathodes to ground potential, a positive potential source connected through a resistor to the anodes of both said first and second electron tubes, a third electron tube with an anode, a grid, and a cathode, said anode being connected to said positive potential source, a voltage divider connected between the grid of said third electron tube and a negative voltage source, a diode having an anode connected to said voltage divider and having a cathode connected to the grid of said first electron tube and to the cathode of said third electron tube, a parallel resistor capacitor combination connected between the anode of said diode and ground, a timing capacitor connected between the anode of said second electron tube and the grid of said first electron tube, a time constant circuit connected between the anode of said first electron tube and the grid of said second electron tube, a resistor connected between the grid of said second electron tube and a negative potential source, the cathode of said second electron tube connected to ground, with the cathode of said first electron tube connected to ground through a resistor, an input terminal and a capacitor connected to the cathode of said first electron tube and a second terminal and a capacitor connected to the grid of said third electron tube.

References Cited UNITED STATES PATENTS 3,021,486 2/1962 Korf et al. 328-58 ARTHUR GAUSS, Primary Examiner.

H. A. DIXON, Assistant Examiner.

U.S. Cl. X.R. 328-207