SU898595A1 - Self-ocsillating multivibrator - Google Patents

Description

The invention relates to a pulse technique and can be used as a stable master pulse generator with increased duty cycle.

A symmetric self-oscillating multivibrator based on logic integrated circuits is known, containing two logic elements, two diodes, two capacitors and two resistors ^]. ’

However, this device has low stability and pulse duty cycle.

Closest to the proposed invention is a multivibrator, in self-oscillating mode, containing two AND-NOT gates, the first input of the first AND gate through the resistor is connected to its output and the first input of the second AND gate, and through the capacitor to the output the second logical element AND NOT [/ 2].

The disadvantage of this scheme is the low stability of the pulse repetition period with high duty cycle.

The purpose of the invention is to increase the stability of the pulse repetition period with high duty cycle.

This goal is achieved by the fact that in a self-oscillating multivibrator containing two AND-NOT gates, the first input of the first AND gate through the resistor is connected to its output and the first input of the second AND gate, and through the capacitor to the output of the second logic gate · AND-NOT element, the first and second diodes, the second capacitor and the third logical element AND, the second input of which through the second capacitor is connected to its output and the second input, the second logical element AND-NOT, the first input of the third ogicheskogo AND-NO element via a second diode connected to the second input thereof and the output of the first NAND gate NAND, and a first input of the first logic AND-NO element via a first diode connected to a second of its WMOs, home and output of the second AND gate NOR.

In FIG. I shows a functional diagram of a self-oscillating multivibrator; in FIG. 2 is a timing diagram explaining the operation of the device.

Self-oscillating multivibrator, second 2 and third logical elements NAND, first and second 5 capacitors, first and second 7 diodes and resistor 8.

The first input of the AND gate is NOT connected through a capacitor 4 to diode 6 with its second input and contains the first I

I and the progress of the logic element 2 AND-NOT, and also through the resistor 8 - with the output of the logic element I AND-NOT, the first input of the logic element 2 AND-NOT and the first input of the logic element ° 3 AND-NOT. The second input of the third logical element through the diode 7 is connected to its first input, and through the capacitor 5 - · with its output and the second input of the logical element 2 AND NOT.

Self-oscillating multivibrator works as follows.

Suppose that in the initial state, logic element 1 is H-NOT included, on. the output voltage corresponds to a logical zero (1 ^ 2 = 4 °) · Therefore, logic elements 2 and 3 are NOT switched off. At their outputs, the voltage of the logical unit (C_ = U ^r ) is set. The capacitor 5 is charged through an open diode 7 to the level U ¹ , and the capacitor 4 is charged through the circuit: the output of the logic element 2 AND-NOT, the capacitor 4, the resonator 8, the output of the logic element 1 AND-NOT. As the capacitor 4 charges, the voltage at the first input of the logic element 1 AND NOT decreases, and when the value ϋ ^ ρΟΗ is reached, it turns off. As a result of this, the AND-NOT logic element 2 is turned on (Uy = U), and the diode 7 is locked.

Initially, due to the input leakage current, the voltage supply at the second input of the AND-NOT logic element 3 increases to the level C ^ -Logic element 3 AND-NOT switches into active mode, and the negative feedback circuit (00с) is closed through capacitor 4.

Subsequently, the capacitor 5 is discharged with almost constant current, the voltage Id decreases linearly.

When the voltage 1) q reaches a value, the Tsfrpogichesky element 2 turns OFF AND NOT. A positive voltage surge from the output of the logic element 2 AND-NOT is transmitted to the inputs of the logic element 1 AND-NOT, the latter is turned on.

sy are repeated.

The pulse duration (determined by the time * ~ - 4, and the interval between pulses (¾) is determined by the discharge time of the capacitor 5. If we neglect the small output resistance of the logic elements, then the pulse repetition period can be defined as

T-t * * +. -game tsip-aise + uch _

In the future, after charging the capacitor

4;

5; pita ^and 4

MUun-) where Cd is the capacitance of the capacitor; Su is the capacitor of the capacitor U is the voltage of the source;

C ^ - voltage drop at the open base-emitter junction; voltage drop on diode 6 at the operating point; the resistance of the resistor in the base circuit of a multi-emitter transistor;

Rg is the resistance of the resistor 8; K is the dimensionless coefficient (for transistor-transistor logic elements KX.0.9);

£ - voltage unlocking diode 7.

An analysis of formula (1) shows that instability of the supply voltage and temperature changes have an insignificant effect on the pulse repetition period. This is because the time ^ is practically independent of destabilizing factors, and the influence of the change in ty is small due to the large duty cycle of the generated pulses (^ << 1 ^.

Thus, this self-oscillating multivibrator, in comparison with the known one, has a greater stability of the pulse repetition period with a high duty cycle.

Claims (2)

The invention relates to a pulse technique and can be used as a stable master oscillator of a pulse train with a high duty cycle. Known symmetric self-oscillating multivibrator based on logic integrated circuits, containing two logic elements, two diodes, two capacitors and two resistors l. However, this device has a low stability and duty cycle. Closest to the proposed invention is a multivibrator, in self-oscillating mode, containing two logical elements AND-NOT, the first input of the first logical element AND-NOT through a resistor is connected to its output and the first input of the second logical element AND-NOT, and through a capacitor vspodom second logical element. The disadvantage of this scheme is the low stability of the UMnynbcoB follow-up period with a high duty cycle. The purpose of the invention is to increase the stability of the period of pulses with a high duty cycle. The goal is achieved by the fact that in a self-oscillating multivibrator containing two NAND logic elements, the first input of the first NAND logic element is connected via a resistor to its output and the first input of the second NAND logic element, and through a capacitor to the output of the second logical - NAND element, the first and second diodes are introduced, the second capacitor and the third NAND logic element, the second input of which is connected via the second capacitor to its output and the second input of the second NAND logic element, the first input is the third I-NOT logic element through the second diode is connected to its second input 38 and the output of the first NAND logic element, and the first input of the first NAND logic element is connected through the first diode to its second input and output of the second I-N logic element. NOT. FIG. 1 shows a functional diagram of a self-oscillating multivibrator; in fig. 2 - timing diagrams for the operation of the device. The self-oscillating multivibrator contains the first 1, second 2 and third 3AGI logical elements, the first 4 and second 5 capacitors, the first 6 and second 7 diodes and a resistor 8. The first input of the logic element 1 AND-NOT is connected through a capacitor 4 and a diode 6 to its second the input and output of the logical element 2 AND-NOT, also through the resistor 8 - with the output of the logical element 1 AND-NOT, the first input of the logical element 2 AND-NOT the first input of the logical element 3 AND-NOT. The second input of the third logic element through the diode 7 is connected, it is connected with its first input, and through the capacitor 5 -. with its output and the rotary input of the logical element 2 NAND. Self-oscillating multivibrator works as follows. Suppose that in the initial state the logical element 1 is H-NOT enabled, on. the output voltage corresponds to a logical zero (2 IJ) Therefore, logic elements 2 and 3 are NOT AND turned off. The voltage of the logical unit (IU and. And) is set at their outputs. The capacitor 5 is charged through the open diode 7 to the level U, and the capacitor 4 is charged along the circuit: the output of the logic element 2 is AND-NOT, the capacitor 4, and the output of the logic element 1 AND-NOT. As the capacitor 4 is charged, the voltage at the first input of the logic element 1 decreases AND-NOT, and upon reaching the value it turns off. As a result, the logical element 2 AND-NOT () is turned on, and the diode 7 is closed. Initially, due to the input leakage current. The voltage at the second input of the logical element 3 AND-NOT increases to the level of the logical element 3 AND-NOT goes into active mode, and through the capacitor 5 closes the negative feedback circuit (OOS). Subsequently, the capacitor 5 is discharged with almost constant current, the voltage U y of 5 is lost. When the voltage (L reaches Vep 1) the ohmic element 2 AND-NOT turns off. A positive voltage spike from the output of a logical element 2 is AND-NOT transmitted to the inputs of the logical element 1 AND-NOT, the latter being turned on. In the following, the popeses are repeated. The pulse duration () is determined by the charge time of the capacitor 4, and the interval between the pulses (t) is determined by the discharge time of the capacitor 5. If we ignore the small output impedance of the logic elements, then the pulse duration can be defined as T -.- tt -and s p Hn-2UE3- Ufe m hgcc and 2 u, CsRgi (UHn-2Ug9-to) KShip-Zie-e) where Cd is the capacitance of capacitor 4; C ..- capacitor capacitance 5; . .5 U - power supply voltage; and - voltage drop on the open .V volume base-emitter junction; and - voltage drop across diode 6 at the operating point; R.- resistance of the resistor in the circuit of the base of the Multi-emitter transistor; Rg is the resistance of the resistor 8; K is a dimensionless coefficient (for transistor-transistor logic elements KiO, 9); - unlocking voltage of diode 7. Analysis of the formula (l) shows that the instability of the supply voltage and temperature changes have little effect on the pulse duration. This is due to the fact that time is practically independent of destabilizing factors, and the effect of ty change is small due to the large duty cycle of the generated pulses (tt | tyj. Thus, this self-oscillating multivibrator has a higher pulse duration Formula of the Invention A self-oscillating multivibrator containing two NAND gates, the first input of the first NAND gate through a resistor is connected to its output and the first input of the NI logical gate, and through a capacitor, with the output of the second H-HEj logic element, characterized in that, in order to increase the stability of the pulse period with a high duty cycle, the first and second diodes, the second capacitor and the third logic element are introduced into it 5 whose second input through the second capacitor is connected to its output and the second input of the second logical element AND-NOT, the first input of the third logical element AND-NOT through the second diode is connected to its second input and output of the first logical element ment AND-NO, and the first input of the first logic AND-NO element is connected via a first diode to the second input thereof and the output of the second AND gate NOR. Sources of information taken into account in the examination I.Gutnikov V.S. Integral electronics in meters. L., Energil, 1974, p. 112 2. For Germany and Germany 1809207, cl. H 03 K 3/282, 1975 (prototype). Py L tui