CD4047 Mono-stable/A-stable Multi-vibrator

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The CD4047B is capable of operating in either the monostable or astable mode. The IC is made by using the Complementary MOS (CMOS) technology, integrated with p-type and n-type enhancement moe transistors. It requires an external capacitor and an external resistor (between pins 2 and 3) to determine the output pulse width in the monostable mode, and the output frequency in the astable mode. Astable operation is enabled by a high level on the astable input or a low level on the astable input. Monostable operation is obtained when the device is triggered by LOW-to-HIGH transition at + trigger input or HIGH-to-LOW transition at − trigger input. The output of the IC always comes in TTL which makes it easy to work with other TTL devices and microcontrollers.

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Monostable Multivibrator

A monostable multivibrator (MMV), often called a one-shot multivibrator, is a pulse generator circuit in which the duration of the pulse is determined by the R-C network, connected externally to the 555 timers. In such a vibrator, one state of output is stable while the other is quasi-stable (unstable). For auto-triggering of output from a quasi-stable state to a stable state, energy is stored by an externally connected capacitor to a reference level. The time taken in storage determines the pulse width.

Astable Multivibrator

An astable multivibrator is a free-running oscillator that switches continuously between its two unstable states. With no external signal applied, the transistors alternately switch from cutoff to saturation state at a frequency that RC time constants of the coupling circuit determine. If these time constants are equal (R and C are equal) then a square wave will generate with a frequency of 1/1.4 RxC. Hence, an astable multivibrator is also a pulse generator or a square wave generator.

CD4047 Key Features

Wide supply voltage range: 3.0V to 15V
High noise immunity: 0.45 VDD (typ.)
Low power TTL compatibility: Fan out of 2 driving 74L or 1 driving 74LS

Special Features

Low power consumption: special CMOS oscillator configuration
Monostable (one-shot) or astable (free-running) operation
True and complemented buffered outputs
Only one external R and C required

Monostable Multivibrator

Positive- or negative-edge trigger
Output pulse width independent of trigger pulse duration
Retriggerable option for pulse width expansion
Long pulse widths possible using small RC components by means of external counter provision
Fast recovery time essentially independent of pulse width
Pulse-width accuracy maintained at duty cycles approaching 100%

Astable Multivibrator

Free-running or gatable operating modes
50% duty cycle
Oscillator output available
Good astable frequency stability
- typical= ±2% + 0.03%/°C @ 100 kHz
- frequency= ±0.5% + 0.015%/°C @ 10 kHz
- deviation (circuits trimmed to frequency VDD = 10V ±10%)

CD4047 Pinout

Pin No	Pin Name	Description
1	C	connect external capacitor
2	R	connect external resistor
3	RC-COMMON	connecting resistor and capacitor
4	A-STB’	Low when used in Astable mode
5	ASTB	High when used in Astable mode
6	– TRIGGER	Monostable mode we give High to Low transition
7	VSS	source supply
8	+TRIGGER	Monostable mode we give Low to High transition
9	EXT RESET	Its an external reset pin
10	Q	high output
11	Q’	low output
12	RETRIGGER	Used in Monostable mode to simultaneously retrigger +trigger and –trigger pin
13	OSC-OUT	oscillated output
14	VDD	Drain supply