CD4047 CMOS Low Power Monostable/Astable Multi-vibrator IC

Pin Configuration

Pin No.
Pin Name
Description

1
C
Used to connect external capacitor

2
R
Used to connect external resistor

3
RCC
Common pin for connecting resistor and capacitor to it

4
AST’(Astable bar)
Low when used in Astable mode

5
AST
High when used in Astable mode

6
-Trigger
When used in Monostable mode we give High to Low transition to this pin

7
Vss
Ground pin of IC

8
+Trigger
When used in Monostable mode we give Low to High transition to this pin

9
EXT RESET
It’s an external reset pin. By giving a high pulse to this pin, it resets the output Q to low and Q’ to high

10
Q
Give normal high output

11
Q’
Inverse output of pin 10, means it gives low output

12
Retrigger
Used in Monostable mode to simultaneously retrigger +trigger and –trigger pin

13
OSC Out
Gives oscillated output

14
Vdd
Positive input pin of IC

Features

Power Consumption is low
Provide Monostable (one-shot) and Astable (free running) operation
High noise immunity
Only one resistor and capacitor required externally
Standardized, symmetrical output characteristics

Monostable Features

Retriggerable option for pulse width expansion
Positive and negative edge trigger
Output pulse width independent of trigger pulse duration

Astable Features

Free running operating modes
50% duty cycle
Oscillator output available
Astable frequency stability is good

Where to use 4047 IC?
We can use the IC in both Astable and Monostable mode, for making different circuit. The IC can be used for generating clock pulse, sine wave, square wave and many others. It can also be used in application of timing delay circuits, frequency multiplier and frequency divider. To generate an envelope signal from the original signal this IC is helpful.

How to use 4047 IC?
It needs an external resistor to be connected between PIN 1 and 3 to determine the output pulse width in Monostable mode. For determining Output frequency in Astable mode it needs a capacitor to be connected between PIN 2 and 3.
Astable mode
If you want to use the IC in Astable mode you need to HIGH the PIN 5 and LOW the PIN 4. So that you will be able to get constantly fluctuating output between HIGH and LOW.
The formula for finding the value of oscillated output frequency (from PIN 13) mathematically is:
OSC Out Frequency= 1 / 4.4RC
Formula for finding the pulse duration is:
t = 2.48RC

Monostable mode
If you want to use the IC in Monostable mode you have to use the +trigger and –trigger PIN. By giving Low to High transition at +trigger PIN and High to Low transition at –trigger PIN you wil be able to get a Monostable output.
The formula for finding the value of frequency mathematically at PIN 11 and 10 is:
F = 1 / 8.8RC

Applications