US3108196A

US3108196A - Constant amplitude and pulse width monostable multivibrator

Info

Publication number: US3108196A
Application number: US37293A
Authority: US
Inventors: Ralph J Colao
Original assignee: General Precision Inc
Current assignee: General Precision Inc
Priority date: 1960-06-20
Filing date: 1960-06-20
Publication date: 1963-10-22
Anticipated expiration: 1980-10-22

Description

Oct. 22, 1963 R. J. COLAO 3,108,196

CONSTANT AMPLITUDE AND PULSE WIDTH MONOSTABLE MULTIVIBRATOR Filed June 20. 1960 [8- CLOCK INVENTOR. RALPH J. COLAO ATTORNEY.

United States Patent C) 3,108,196 CUNSTANT AMPLITUDE AND PULSE WIDTH MONTAELE MULTIVIBRATOR Ralph J. Colao, White Plains, NFL, assigucr to General Precision, Inc, a corporation of Delaware Filed June 20, 1969, Ser. No. 37,293 8 Claims. (til. 307-3155) This invention relates to multivibrators and more particularly to monostable multivibrators which are suitable for use in digital logic and computer circuits.

In digital logic and computer applications it is very often necessary to have a well regulated source of pulses which are an accurate analogue of the computer or master clock pulses. These pulses must not vary in amplitude or length and must have sharp leading and trailing edges. Furthermore, the multivibrator which generates these pulses must be isolated electrically from stray pulses Which would otherwise trigger the multivibrator and cause a false output. Many of the above requirements can be met by using high quality components along with careful construction techniques and adequate shielding. However, such a solution is impractical in view of the large number of these multiv-ibrators employed in a modern digital device and the increased costs attendant such a solution.

One object of this invention is to provide a monostable multivibrator which in response to trigger or clock pulses supplies a correspondingly pulsed output in which each individual pulse is uniform in magnitude and duration and has sharp leading and trailing edges.

Another object of this invention is to provide a monostable multivibrator which is capable of providing well regulated output pulses in response to high frequency clock or trigger pulses.

A further object of the invention is to provide a monostable multivibrator which is reliable in operation and readily and easily constructed from standard compo nents.

The invention contemplates a monostable multivibrator circuit comprising a pair of electron valves each having at least one control and one output electrode and being biased so that one of the valves is normally on or conducting while the other valve is normally off or nonconducting. A first electric storage means which receives the clock or trigger pulses is connected to the control electrode of the said one valve by a first asymmetric conducting means to provide for extinguishing the one valve output whenever a clock or trigger pulse is applied to the first storage means. Means are provided for connecting the output electrode of the one valve to the control electrode of the said other valve which turns on or conducts when the one valve is turned oil. or becomes nonconductive. A second electric storage means is connected to the output electrode of the other valve and to the control electrode of the one valve and to a constant current source which discharges the second storage means at a controlled rate, by another asymmetric conductor. Charging means are connected to the second storage means for charging said means to a predetermined value whenever it has been discharged by the constant current source.

The foregoing and other objects and advantages of this invention will be more apparent from a consideration of the specification and drawing wherein one embodiment of the invention is described and shown in detail for illustration purposes only.

The single FIGURE is a schematic circuit diagram of a monostable multivibrator circuit constructed in accordance with the invention.

In the drawing, clock pulses from a source not shown are applied to a terminal 1 which is connected to the anode of a diode 3. The cathode of diode 3 is connected to one side of a capacitor 4 and the common junction of diode 3 and capacitor 4 is connected to a negative voltage supply terminal 6 by a resistor 7. The other side of capacitor 4 is connected to negative voltage supply 6 by a resistor 8.

A diode 9 has its anode connected to the common junction of resistor 8 and capacitor 4 and its cathode to the base 10 of a transistor 12. Another diode 14 has its cathode connected to the common junction of resistor 8 and capacitor 4 and its anode connected to ground by a capacitor 15. A voltage divider comprising two series connected

resistors

17 and 18 is connected between ground and another negative voltage supply terminal 19 and the common junction of

resistors

17 and 18 is connected to the anode of diode 14 which places a biasing potential on the anode of diode 9 to prevent stray positive pulses or noise voltages from afiecting transistor 12.

The emitter 20 of transistor 12 is connected directly to ground and the collector 21 is connected to voltage supply terminal 6 by a resistor 22. Collector 21 is also connected to the base 24 of transistor 25 by a compensating attenuator network 26 which network comprises a resistor 27 and a capacitor 28 connected in parallel between the collector 21 and the base 24. Network 26' matches the input impedance of transistor 25 and the output impedance of transistor 12 to provide the fastest possible rise time. Base 24 is also connected to a positive voltage supply terminal 30 by resistor 31 and the emitter 32 of transistor 25 is connected directly to ground.

The collector 33 of transistor 25 is connected to: a tenninal 34 to which the output of the circuit may be connected. Terminal 34 is connected to voltage source terminal 6 by a resistor 35. A series connected resistor 36 and a Zener diode 37 are connected between source terminal 6 and ground and the common junction of the resistor and diode is connected to terminal 34 by a diode 38 which has its anode connected to the common junction and its cathode connected to terminal 34.

A resistor 40, a capacitor 41, a diode 42 and another resistor 43 are connected in series between source terminal 6 and ground. The common junction of resistor and capacitor 41 is connected to terminal 34 by a diode 45 which has its cathode connected to the common junction and its anode connected to terminal 34. The common junction of capacitor 41 and diode 42 is connected to the base 10 of transistor 12 by a diode 46 which has its cathode connected to base 10 and its anode connected to the common junction of capacitor 41 and diode 42. The diode 42 is connected so that its cathode and the anode of diode 46 are connected to the same common point. Base Ill of transistor 12 is connected to voltage source terminal 19 through a transistor 48 and an adjustable resistor 49.

The collector 50 of transistor 48 is directly connected to the base 10 and the emitter 51 is connected through variable resistor 49 to source 19.

The base 52 of transistor 48 is connected to ground by a resistor 53 and to source terminal 19 by a Zener diode 54 to provide a substantially constant voltage on the base 52. The collector 21 of transistor 12 is also connected to source 19 by a diode 56 which has its cathode connected to collector 21 and its anode connected to the source terminal 19.

In operation negative clock pulses applied to terminal 1 charge capacitor 4 to a negative voltage which is comparable to the voltage of the clock pulse. When the clock pulse returns to its Zero voltage level, capacitor 4 discharges through diode 9 which causes the base 10 of transistor 12 to become positive and, thus, prevents further conduction through transistor 12. The negative voltage swing of the collector 21 of transistor 12 is applied to the base 24 of transistor 25 through the compensating attenuating network 26. This negative voltage turns transistor 25 on to institute the monostable multivibrator action. When transistor 25 is turned on, the charge on capacitor 41 is transferred to the base 10 of transistor 12 and maintains it in the off condition. However, at the same time, capacitor 41 is discharged through the constant current source which is comprised of transistor 43, adjustable resistor 49, resistor 53 and Zener diode 54.

The rate at which condenser 41 is discharged through the constant current source will be a function of variable resistor 49 and an adjustment of this resistor will vary the length of the pulses output at terminal 34. The entire circuit will return to the original or starting state, that is, with transistor 12 conducting and transistor 25 cut off when the charge on capacitor 41 diminishes to zero. When this condition is obtained, the constant current source then supplies biasing current to the base 19 of transistor 12. When transistor 12 conducts, capacitor 41 will recharge to the negative voltage it had previously attained through resistor 43, diode 42 and resistor 49.

Diode 46 prevents positive voltage from capacitor 4 from affecting the charge on capacitor 41. Thus, the pulse length of the multivibrator is unaffected by variations in the amplitude of the clock pulse applied to terminal 1. In order that initial conditions, that is those conditions prevailing prior to the application of a clock pulse at the terminal 1, remain constant with respect to capacitor 41, the Zener diode 37 clamps the terminal 34 at a constant voltage level.

Another of the features of this circuit is the effect produced by diode 45 which prevents cross-coupling capacitor 41 from affecting the sharpness of the trailing edge of the output wave form since it decouples the capacitor from the collector load resistor 35 during this critical period.

The circuit described has been constructed so as to provide output voltages which switch between l volts and -O.2 volt. The following values will provide this output. With reference to the variable resistor 49, the values given in the table range from 3.9 to 7.5K ohms to provide the exact pulse length required.

Voltages 6 volts 28 19 do l0 3t) do +16 Clock do Resistors 17 ohms 270 43 do 470 1K do 1.5

K

22,35, 36 do 2.7K 27 do 3.3K

Although only one embodiment of the invention has been shown and described in detail for illustration pur poses, it is to be expressly understood that the invention is not to be limited thereto.

What is claimed is:

1. A monostable multivibrator circuit comprising, a pair of electron valves each having at least one control and one output electrode, said valves being biased such that one valve is normally on or conducting and the other is normally off or nonconducting, first electric storage means for receiving triggering pulses, first asymmetric conducting means for connecting the first electric storage means to the control electrode of the said one valve to extinguish conduction when a triggering pulse is applied to the first electric storage means, means for connecting the output electrode of the said one valve to the input electrode of the said other valve to turn the said other valve on when the said one valve is turned off, second electric storage means connected to the output electrode of the said other valve and by an asymmetric conductor, which is arranged to oppose the conduction from the first electric storage means, to the control electrode of the said one valve and to a constant current source which discharges said second storage means at a controlled rate, and means for charging said second storage means to a predetermined value each time it is discharged by the said constant current source.

2. A monostable multivibrator circuit comprising a pair of transistors each having one control and one output electrode, said transistors being biased such that one is normally on or conducting and the other is normally oil or nonconducting, first asymmetric conducting means for connecting a first storage means to the control electrode of the said one transistor to extinguish conduction Whenever a triggering pulse is applied to the first electric storage means, means for connecting the output electrode of the said one transistor to the control electrode of the said other transistor to turn the said other transistor on when the said one transistor is turned off, second electric storage means connected to the output electrode of the said other transistor and by an asymmetric conductor, which is arranged to oppose the conduction from the first electric storage means, to the control electrode to the said one transistor and to a constant current source which discharges the second storage means at a predetermined rate, and means for recharging the second storage means after it has been discharged by said constant current source.

3. A monostable multivibrator circuit as set forth in claim 1 in which the transistors are connected such that the base is the control electrode and the collector is the output electrode.

4. A monostable multivibrator circuit as set forth in claim 1 in which said first and second electric storage means are condensers and the asymmetric conducting means are diodes.

5. A monostable multivibrator circuit comprising a pair of transistors which are biased so that one is normally on or conducting and the other is normally off or nonconducting, a first capacitor for receiving triggering pulses, a diode connecting the first capacitor to the base of the said one transistor to extinguish conduction when the triggering pulse is applied to the first capacitor, means for connecting the collector of the said one transistor to the base of the said other transistor to turn the said other transistor on when said one transistor is turned off, a second capacitor connected to the collector of the said other transistor and by a diode, which is arranged to oppose the conduction from the first capacitor, to the base of the one tnansistor and to a constant current source which discharges the second capacitor at a controlled rate, and means for charging the second capacitor to a predetermined value each time it is discharged by the constant current source.

6. A monostable multivibrator circuit as set forth in claim 5 in which the means for charging the second capacitor comprises a resistive network and a diode connected in series with the capacitor to a voltage source.

7. A monostable multiviorator circuit comprising a pair of transistors which are biased so that one is normally on or conducting and the other is normally off or noncondncting, a first capacitor for receiving triggering pulses, a diode connecting the first capacitor to the base of the said one transistor to extinguish conduction when the triggering pulse is applied to the first capacitor, means for connecting the collector of the said one transistor to the base of the said other transistor to turn the said other transistor on when said one transistor is turned off, a diode for connecting the collector of the second transistor to a second capacitor, another diode, which is arranged to oppose the conduction from the first capacitor, connecting said second capacitor to the base of the one transistor and to a constant current source which discharges the second capacitor at a controlled rate, and means for charging the second capacitor to a predetermined value each time it is discharged by the constant current source.

8. A monostable multivibrator circuit as set forth in claim 7 in which the means for charging the second capacitor comprises a resistive network and a diode connected in series with the capacitor to a voltage source.

References Cited in the file of this patent UNITED STATES PATENTS 2,827,574 Schneider Mar. 18, 1958 2,90i1,6'39 Woll Aug. 25, 1959 2,976,428 Parkhill et a1. Mar. 21, 1961 2,976,432 Geckle Mar. 21, 1961 2,986,649 Wray May 30, 1961

Claims

1. A MONOSTABLE MULTIVIBRATOR CIRCUIT COMPRISING, A PAIR OF ELECTRON VALVES EACH HAVING AT LEAST ONE CONTROL AND ONE OUTPUT ELECTRODE, SAID VALVES BEING BIASED SUCH THAT ONE VALVE IS NORMALLY ON OR CONDUITING AND THE OTHER IS NORMALLY OFF OR NONCONDUCTING, FIRST ELECTRIC STORAGE MEANS FOR RECEIVING TRIGGERING PULSES, FIRST ASYMMETRIC CONDUCTING MEANS FOR CONNECTING THE FIRST ELECTRIC STORAGE MEANS TO THE CONTROL ELECTRODE OF THE SAID ONE VALVE TO EXTINGUISH CONDUCTION WHEN A TRIGGERING PULSE IS APPLIED TO THE FIRST ELECTRIC STORAGE MEANS, MEANS FOR CONNECTING THE OUTPUT ELECTRODE OF THE SAID ONE VALVE TO THE INPUT ELECTRODE OF THE SAID OTHER VALVE TO TURN THE SAID OTHER VALVE ON WHEN THE SAID ONE VALVE IS TURNED OFF, SECOND ELECTRIC STORAGE MEANS CONNECTED TO THE OUTPUT ELECTRODE OF THE SAID OTHER VALVE AND BY AN ASYMMETRIC CONDUCTOR, WHICH IS ARRANGED TO OPPOSE THE CONDUCTION FROM THE FIRST ELECTRIC STORAGE MEANS, TO THE CONTROL ELECTRODE OF THE SAID ONE VALVE AND TO A CONSTANT CURRENT SOURCE WHICH DISCHARGES SAID SECOND STORAGE MEANS AT A CONTROLLED RATE, AND MEANS FOR CHARGING SAID SECOND STORAGE MEANS TO A PREDETERMINED VALUE EACH TIME IT IS DISCHARGED BY THE SAID CONSTANT CURRENT SOURCE.