Lycée ManginSarrebourg Terminale STI Multivibrateurs Astables Chapitre n° 6 TP cours Année Scolaire Tutorial providing good stuff on timer its pin configuration,internal working, Modes of operation(astable,Monostable,Bistable),timeconstant. Astable Multivibrator Using Transistor | See more ideas about Variables, Arduino and Circuit diagram.

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Thus the gate may comprise a single non-inverting gate, with the output for subsequent circuitry being taken from output terminal 16′ instead of terminal 18′ as shown on the drawing. The capacitors are ‘discharged’ so no current is flowing in them: The circuit according to claim 3 wherein said predetermined voltage level is higher than the highest level normally provided at said “nor” output in the absence of said astablr gate by the highest voltage astablf present across said timing capacitor.

It is accordingly an object of the present invention to provide improved multivibrator circuitry employing standard integrated circuit gate devices.

4QD-TEC: Multivibrators and Relaxation Oscillator Circuits

Circuit elements in series can be re-arranged, their order is not important. Since the voltage at output terminal 18 is now relatively positive, capacitor 24 charges through resistors 22 and 20 as illustrated at 28 in FIG.

The conditions at time t 3 are identical to those at time t 1and the cycle repeats. The way you draw a circuit is important. Nevertheless it remains a sstable and instructive exercise!

Meaning of “multivibrateur” in the French dictionary

Click for automatic bibliography generation. The apparatus according to claim 3 wherein said means coupling an output of said second gate to the “nor” output of the first mentioned gate comprises a voltage divider disposed between positive and negative voltage points and having a first tap coupled to the said output of said second gate, and diode means coupling the “nor” output of the first mentioned gate to a more positive voltage tap on said voltage divider, said diode having its anode coupled to the last mentioned tap.


The apparatus according to claim 8 wherein said transistors forming said gate circuit are provided within a common semiconductor integrated circuit structure. When capacitor 24 discharges past the level atsable the bias voltage supplied to the base of transistor 36, transistor 34 tends to cease conduction whereby the voltage drops at the emitter thereof.

P BAC Cours

If you try and put a larger reverse voltage on the base – the transistor base emitter junction conducts like a zener diode. The voltage drop across resistor 38 turns off transistor 36 at its emitter, while the voltage drop across resistor 40 lowers the voltage at the base of transistor 46 and causes the emitter of transistor 46 to lower the voltage level at terminal 18 to a relatively negative value. An astable multivibrator circuit comprising: But in most two transistor multivib circuits it is possible fours replace one of the transistors by its complement i.

Search Expert Search Quick Search. There are also a lot of other oscillator circuits which aren’t quite conventional multivibs or relaxation oscillators.

Warning This page is going to be long: It is another object of the present invention to provide an improved multivibrator comprising conventional gate circuitry and which is xstable by increased operating speed.

This ‘failure to oscillate’ became common: The voltage at terminal 18 is then again effectively clamped to such high voltage through diode The chain of output pulses may be started and stopped by the disabling-enabling circuitry with a minimum of interference with the desired waveform thereof. The apparatus according to claim 8 wherein said means coupling the output of said one of said transistors to provide said inverted output comprises a first emitter-follower transistor and wherein the means coupling the collector of the second of said transistors to provide said non-inverted output comprises a second emitter-follower transistor, said input means comprising the base terminal of one of said pair of transistors.


This is particularly true for circuits exhibiting high immunity to noise. As will be seen hereinafter, this relatively positive output disables operation of the astable multivibrator. The asymmetrical circuit also is more reliable: Transistor 36 starts conduction, and applies a relatively negative-going excursion on its collector to the base of transistor Then, when input 72 becomes relatively positive for enabling operation of the circuit, terminal 60 drops in potential causing the voltage at the junction between components 66 and 68 to drop whereby diode 70 is disconnected.

According to a preferred form of the present invention, gate 54, when in a disabling mode, maintains the voltage at terminal 18 well above the voltage which would appear at terminal 18 during regular astable multivibrator operation. The only external components required comprise the timing circuitry including capacitor 24 and resistors 20 and The multivibrator according to claim 1 wherein said “or-nor” gate includes a second input terminal, said second input terminal being connected to a bias voltage point.

Also, while gates are spoken of as switching from one condition or state to another, it is not meant to imply that it is common or necessary for a gate to latch itself in one state or another.

Since both transistors conduct simultaneously, the on period is a short pulse followed by a long recovery symptomatic of a relaxation oscillator. The diode isn’t really needed but it does improve the waveform available on the emitters so that a good sawtooth aetable available.

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