4047 IC: A Detailed Introduction To A Monostable and Astable Multivibrator

What is a Multivibrator IC?

A multivibrator is an electronic circuit that generates square wave pulses or oscillations. It is a type of relaxation oscillator that is commonly used in various applications such as timing circuits, pulse generation, and waveform shaping. The 4047 IC is a versatile integrated circuit that can function as both a monostable and astable multivibrator.

Types of Multivibrators

There are three main types of multivibrators:

1. Astable Multivibrator: An astable multivibrator, also known as a free-running multivibrator, continuously oscillates between two states without any external trigger. It generates a continuous stream of square wave pulses.

2. Monostable Multivibrator: A monostable multivibrator, also called a one-shot multivibrator, generates a single output pulse of a fixed duration when triggered by an external input pulse. It remains in its stable state until triggered.

3. Bistable Multivibrator: A bistable multivibrator, also referred to as a flip-flop, has two stable states and can be toggled between them using external triggers. It maintains its state until the next trigger is applied.

4047 IC: Overview and Features

The 4047 IC is a CMOS (Complementary Metal-Oxide-Semiconductor) integrated circuit that can be configured as either a monostable or astable multivibrator. It offers several features and benefits:

• Low power consumption
• Wide supply voltage range (3V to 15V)
• Adjustable pulse width and frequency
• Schmitt trigger inputs for noise immunity
• Complementary outputs
• Compact 14-pin DIP or SOIC package

The 4047 IC consists of the following internal components:

• RS flip-flop
• Schmitt trigger inputs
• Output drivers
• Current mirrors
• Timing capacitor and resistor

Pin Configuration

The 4047 IC has a 14-pin package with the following pin configuration:

Monostable Multivibrator Configuration

To configure the 4047 IC as a monostable multivibrator, follow these steps:

1. Connect the ASTABLE input (pin 3) to VSS (ground).
2. Apply the trigger pulse to the TRIGGER input (pin 4 or 9).
3. Connect a timing capacitor between the THRESHOLD input (pin 5 or 10) and VSS.
4. Connect a timing resistor between the DISCHARGE input (pin 6) and VDD.
5. The output pulse will be available at the Q output (pin 1), and its complementary signal will be available at the /Q output (pin 2 or 13).

The pulse width of the output signal is determined by the values of the timing capacitor (C) and timing resistor (R) according to the following equation:

t = 2.48 × R × C

Where:
– t is the pulse width in seconds
– R is the resistance in ohms
– C is the capacitance in farads

Example Circuit

Here’s an example circuit diagram for a monostable multivibrator using the 4047 IC:

        VDD
         |
        .-.
        | |
        | | R
        | |
        '-'
         |
         |      .-------.
         |      |       |
         '------+       |
                |       |
                |      ,+-.
          .-----+------+4047+------.
          |     |      `+-'       |
          |     |       |         |
          |     '-------+         |
          |             |         |
          |            ,+-.       |
         .+.           | C |      |
  INPUT -+*+-----------+   +------'
         | |           `+-'
         '-'            |
          |             |
         VSS           VSS

In this example, the trigger input is connected to an external input signal, and the timing capacitor (C) and resistor (R) determine the pulse width of the output signal.

Astable Multivibrator Configuration

To configure the 4047 IC as an astable multivibrator, follow these steps:

1. Connect the ASTABLE input (pin 3) to VDD.
2. Connect a timing capacitor between the THRESHOLD input (pin 5 or 10) and VSS.
3. Connect a timing resistor between the DISCHARGE input (pin 6) and VDD.
4. The oscillating output signal will be available at the Q output (pin 1), and its complementary signal will be available at the /Q output (pin 2 or 13).

The frequency and duty cycle of the output signal are determined by the values of the timing capacitor (C) and timing resistor (R) according to the following equations:

f = 1 / (4.4 × R × C)
D = 0.5

Where:
– f is the frequency in hertz
– D is the duty cycle (50% for astable mode)
– R is the resistance in ohms
– C is the capacitance in farads

Example Circuit

Here’s an example circuit diagram for an astable multivibrator using the 4047 IC:

        VDD
         |
        .-.
        | |
        | | R
        | |
        '-'
         |
         |      .-------.
         |      |       |
         '------+       |
                |       |
                |      ,+-.
          .-----+------+4047+------.
          |     |      `+-'       |
          |     |       |         |
          |     '-------+         |
          |             |         |
          |            ,+-.       |
         .+.           | C |      |
        -+-+-----------+   +------'
         | |           `+-'
         '-'            |
          |             |
         VSS           VSS

In this example, the timing capacitor (C) and resistor (R) determine the frequency and duty cycle of the oscillating output signal.

Applications of the 4047 IC

The 4047 IC finds applications in various domains, including:

1. Timing circuits: The monostable configuration can be used to generate precise timing pulses for controlling the duration of events or triggering other circuits.

2. Pulse generation: The astable configuration can be used to generate continuous streams of pulses with adjustable frequency and duty cycle.

3. Waveform shaping: The 4047 IC can be used to convert other waveforms, such as sine waves or triangular waves, into square waves.

4. Frequency division: By cascading multiple 4047 ICs in the astable configuration, frequency division can be achieved to generate lower frequency signals.

5. Debouncing switches: The monostable configuration can be used to debounce mechanical switches by generating a clean output pulse when the switch is pressed, eliminating any unwanted multiple transitions.

FAQ

1. What is the difference between a monostable and astable multivibrator?

2. A monostable multivibrator generates a single output pulse of a fixed duration when triggered, while an astable multivibrator continuously oscillates and generates a continuous stream of pulses without any external trigger.

3. How do I determine the pulse width in a monostable multivibrator using the 4047 IC?

4. The pulse width in a monostable multivibrator is determined by the values of the timing capacitor (C) and timing resistor (R) connected to the THRESHOLD and DISCHARGE inputs of the 4047 IC. The pulse width can be calculated using the equation: t = 2.48 × R × C, where t is the pulse width in seconds, R is the resistance in ohms, and C is the capacitance in farads.

5. Can I adjust the frequency and duty cycle of the output signal in an astable multivibrator using the 4047 IC?

6. Yes, the frequency and duty cycle of the output signal in an astable multivibrator can be adjusted by changing the values of the timing capacitor (C) and timing resistor (R) connected to the THRESHOLD and DISCHARGE inputs of the 4047 IC. The frequency can be calculated using the equation: f = 1 / (4.4 × R × C), where f is the frequency in hertz, R is the resistance in ohms, and C is the capacitance in farads. The duty cycle in astable mode is fixed at 50%.

7. What is the purpose of the ASTABLE input in the 4047 IC?

8. The ASTABLE input (pin 3) in the 4047 IC is used to select the operating mode of the IC. When the ASTABLE input is connected to VSS (ground), the IC operates as a monostable multivibrator. When the ASTABLE input is connected to VDD, the IC operates as an astable multivibrator.

9. Can I cascade multiple 4047 ICs to achieve frequency division?

10. Yes, multiple 4047 ICs can be cascaded in the astable configuration to achieve frequency division. By connecting the output of one 4047 IC to the trigger input of the next 4047 IC, the frequency of the output signal can be divided by a factor of 2 at each stage.

Conclusion

The 4047 IC is a versatile integrated circuit that can function as both a monostable and astable multivibrator. It offers a wide range of applications in timing circuits, pulse generation, waveform shaping, frequency division, and switch debouncing. By configuring the 4047 IC with appropriate timing components, desired pulse widths, frequencies, and duty cycles can be achieved. Understanding the functionality and configuration of the 4047 IC empowers designers and engineers to effectively utilize this multivibrator IC in their projects and applications.