CD4047 Astable multivibrator circuit

Last updated on April 16th, 2022 at 04:28 am

When we say to an astable multivibrator circuit. Most people think of  IC-555. It is famous for making pulse generator and timer. But this time, I recommended, CD4047. It is also an Astable multivibrator circuit on CMOS chip.

We can use it in many circuits. Most used in an AC inverter, Square wave generator, LED flasher, and more. It has an advantage over 555 IC that output a 50% duty cycle and requires a wide voltage supply. (3V to 15V). Do you begin interested?

Let’s learn the basic datasheet, first!

Are you a beginner? Learn Basic Electronics

CD4047 Datasheet

Look below, it looks like CD4011 in DIP-14 form.

Pinout

Next step…Which leg that we enter the power supply? Where is the output pin and more, see below.

Basic Description

Then learn basic usage. See the block diagram below.

We can use the CD4047B either the monostable or astable mode. It is easy to use. With a few external components, capacitor (between pins 1 and 3) and a resistor
(between pins 2 and 3) to determine the output pulse width
in the monostable mode, and the output frequency in the
astable mode.

Learn more: http://www.fairchildsemi.com/

Features

In short

• Wide supply voltage range: 3.0V to 15V
• Noise protection: 0.45 VDD (Typical)
• Low power TTL compatibility
• Low power consumption CMOS oscillator
• Monostable (one-shot) or astable (free-running) operation

Astable Multivibrator

• Free-running 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%)

Difference between 555 & CD4047

First of all, the shape is noticeably different, the NE555 has 8 pins and CD4047 has 14 pins. The CD4047 starts at 3V supply.

If the focus is on the Astable multivibrator circuit. CD4047 requires only 2 devices, Resistor, and Capacitor only.

And more importantly, it has a duty cycle at 50% in a symmetrical standard, no need for additional equipment.

It is therefore suitable for generating a set frequency in inverter circuit.

See: CD4047 inverter circuit

Example Circuits

I know you are interested in this CD4047. Even read a lot of information. But not clear. Let’s learn working example circuits.

Basic Square wave generator

Look at the circuit below.

We use 9-battery is a power supply. The output will be a square wave, which has three forms are:

• I would Get The 50% duty Cycle
• Pin 13 is the basic frequency obtained by the VR1 and C1 across pins 1,2 & 3.
• Pin 10 (Q) and Pin 11(Q) shows the half frequency of the original frequency at pin 13.
• Both frequencies at pins 10 and pin 11 are inverted to each other phase. The inverted Outputs are 180 degrees out of phase.
• Three outputs have the 50% duty cycle.

Thanks: MR OHM 1970 and Hema for great information

See the waveform signal of three output.

We cannot adjust the duty cycle of this circuit. It always is duty cycle of 50% that symmetry exists.

Then, we can set the frequency output by adjusting VR1 and charging C1.

The value of VR1 is used in a range of 1K to 1M. To Adjust to the desired frequency. And, the C1 will determine the frequency. The value used to determine the various range. You can see from the table below.

Note: You should pick a capacitor that has a low leakage. To reduce waveform distortion and mistake frequency.

The value of C1 in the circuit as Figure 1 to determine the frequency use.

• 1uF = 1-10Hz
• 0.1uF = 10Hz-1kHz
• 0.01uF = 100Hz-10kHz

And I use VR1 potentiometer is 250K.

How to build

This project is a few components so can put on the bread board or the universal PCB board.

And be careful with wiring, the polarity of the electrolytic capacitors, Pin of the IC.

Then, measure a waveform at pin 13, pin 10, and pin 11.

The shopping lists

• VR1: The potentiometer, See in text
• C1: See in text
• Semiconductor
  IC1: CD4047, Low Power Monostable Astable Multivibrator
• Other components
  Socket 14 pin, The universal PCB board.

Blinking two LEDs using CD4047

I want you to see a clearer picture of how this IC is used. Let’s build blinking two LEDs using CD4047. We used to use these circuits before, they are simple.

• LED Flashers Circuits and Projects using transistor
• IC 555 LED Flasher
• Blink 2 LED flasher using Arduino

But this IC is also easy to use. See in the circuit below.

We add LED1 (Q) and LED2 (Q) having R1 and R2 limit a safe current for them.

How to build

This circuit can be built easily. We modify previous circuit. Then, add LEDs and Resistors on the breadboard as Figure below.

And…

Test the Blinking LEDs circuit

I want you to try to build this circuit. For children to have fun Try changing the C1 and adjusting VR1. Notice the two LEDs blinking. Look at the video for better visualization and understanding.

Conclusion

In the past, I used the CD4047 as an astable multivibrator circuit only. Many people like to use it in this way as well. However, if in the future I use it in other ways. I will present to you again, please follow

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