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

Introduction to Multivibrator ICs

Multivibrators are essential electronic circuits that generate square waves or rectangular pulses. These circuits find widespread applications in various domains, including timing circuits, pulse generation, and clock signal generation. Among the various types of multivibrators, the 4047 IC stands out as a versatile and commonly used integrated circuit (IC) that can function as both a monostable and astable multivibrator.

In this comprehensive article, we will delve into the details of the 4047 IC, exploring its features, pinout, and applications. We will also discuss the differences between monostable and astable modes of operation and provide practical examples of how to use the 4047 IC in various circuits.

What is a Multivibrator?

A multivibrator is an electronic circuit that generates a square wave or rectangular pulse output. It consists of two amplifying stages connected in a positive feedback loop, causing the output to oscillate between two stable states. The output of a multivibrator switches between a high and low voltage level, creating a square wave or pulse signal.

Multivibrators can be classified into three main categories:

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 square wave output with a fixed frequency determined by the values of the external resistors and capacitors connected to the circuit.

2. Monostable Multivibrator: A monostable multivibrator, also called a one-shot multivibrator, generates a single output pulse of a fixed duration in response to an external trigger signal. Once triggered, the output remains in the unstable state for a predetermined time period before returning to its stable state.

3. Bistable Multivibrator: A bistable multivibrator, or a flip-flop, has two stable states and can be triggered to switch between them using external signals. It remains in one state until a trigger signal causes it to switch to the other state, where it remains until another trigger signal is applied.

4047 IC: Features and Pinout

The 4047 IC is a CMOS (Complementary Metal-Oxide-Semiconductor) integrated circuit that can be configured as either an astable or monostable multivibrator. It offers several features that make it a popular choice for various applications. Let’s explore the key features and pinout of the 4047 IC.

Features of the 4047 IC

1. Dual Functionality: The 4047 IC can be configured to operate as either an astable or monostable multivibrator, providing flexibility in circuit design.

2. Wide Supply Voltage Range: The IC can operate with a supply voltage ranging from 3V to 15V, making it suitable for a variety of applications.

3. Low Power Consumption: Being a CMOS device, the 4047 IC has low power consumption, making it ideal for battery-powered applications.

4. Adjustable Pulse Width and Frequency: The pulse width and frequency of the output signal can be easily adjusted by selecting appropriate values for the external resistors and capacitors.

5. Schmitt Trigger Inputs: The 4047 IC features Schmitt trigger inputs, which provide noise immunity and ensure clean switching of the output signal.

Pinout of the 4047 IC

The 4047 IC comes in a 14-pin dual in-line package (DIP). Here’s the pinout diagram of the 4047 IC:

         +--------------+
   Q     |1           14| VDD
   Q     |2           13| RTC
   QN    |3           12| RTCN
   QN    |4           11| ASTABLE
   RTC   |5           10| REXT/CEXT
   RTCN  |6            9| R
   GND   |7            8| C
         +--------------+

1. Q (Pin 1): Output signal in astable mode, high impedance in monostable mode.
2. Q (Pin 2): Complementary output signal in astable mode, high impedance in monostable mode.
3. QN (Pin 3): Inverted output signal in astable mode, low impedance in monostable mode.
4. QN (Pin 4): Inverted complementary output signal in astable mode, low impedance in monostable mode.
5. RTC (Pin 5): Retrigger input for monostable mode, retrigger clear for astable mode.
6. RTCN (Pin 6): Retrigger input for monostable mode, retrigger clear for astable mode.
7. GND (Pin 7): Ground connection.
8. C (Pin 8): Capacitor connection for timing.
9. R (Pin 9): Resistor connection for timing.
10. REXT/CEXT (Pin 10): External resistor or capacitor connection for timing.
11. ASTABLE (Pin 11): Mode selection input. Connect to VDD for astable mode, GND for monostable mode.
12. RTCN (Pin 12): Retrigger input for monostable mode, retrigger clear for astable mode.
13. RTC (Pin 13): Retrigger input for monostable mode, retrigger clear for astable mode.
14. VDD (Pin 14): Positive supply voltage.

Astable Mode Operation

In astable mode, the 4047 IC functions as a free-running multivibrator, continuously generating a square wave output without any external trigger. The frequency and duty cycle of the output signal are determined by the values of the external resistor (R) and capacitor (C) connected to pins 8 and 9, respectively.

Astable Mode Configuration

To configure the 4047 IC in astable mode, follow these steps:

1. Connect the ASTABLE pin (pin 11) to VDD.
2. Connect an external resistor (R) between pin 9 and VDD.
3. Connect an external capacitor (C) between pin 8 and GND.
4. The output square wave will be available at pins 1 (Q) and 2 (Q).

The frequency (f) and period (T) of the output square wave can be calculated using the following formulas:

f = 1 / (4.4 * R * C)
T = 4.4 * R * C

where:
– f is the frequency in Hz
– T is the period in seconds
– R is the resistance in ohms (Ω)
– C is the capacitance in farads (F)

By selecting appropriate values for R and C, you can adjust the frequency and period of the output square wave to suit your application requirements.

Astable Mode Timing Diagram

Here’s a typical timing diagram for the 4047 IC in astable mode:

        +------+      +------+      +------+
  Q     |      |      |      |      |      |
        |      |      |      |      |      |
        +      +------+      +------+      +------
           T/2     T/2    T/2     T/2    T/2 

        +------+      +------+      +------+
  Q     |      |      |      |      |      |
        |      |      |      |      |      |
        +      +------+      +------+      +------
           T/2     T/2    T/2     T/2    T/2

The output square wave has a 50% duty cycle, meaning that the high and low states have equal durations (T/2). The period (T) of the waveform is determined by the values of R and C, as mentioned earlier.

Monostable Mode Operation

In monostable mode, the 4047 IC generates a single output pulse of a fixed duration in response to an external trigger signal. The pulse width is determined by the values of the external resistor (R) and capacitor (C) connected to pins 8 and 9, respectively.

Monostable Mode Configuration

To configure the 4047 IC in monostable mode, follow these steps:

1. Connect the ASTABLE pin (pin 11) to GND.
2. Connect an external resistor (R) between pin 9 and VDD.
3. Connect an external capacitor (C) between pin 8 and GND.
4. Apply the trigger signal to either the RTC (pin 5) or RTCN (pin 6) input.
5. The output pulse will be available at pins 3 (QN) and 4 (QN).

The pulse width (tw) of the output pulse can be calculated using the following formula:

tw = 2.48 * R * C

where:
– tw is the pulse width in seconds
– R is the resistance in ohms (Ω)
– C is the capacitance in farads (F)

By selecting appropriate values for R and C, you can adjust the pulse width to meet your application requirements.

Monostable Mode Timing Diagram

Here’s a typical timing diagram for the 4047 IC in monostable mode:

        +-------+     +-------+     +-------+
Trigger |       |     |       |     |       |
        |       |     |       |     |       |
        +       +-----+       +-----+       +-----

         +------------+           +------------+
  QN     |            |           |            |
         |            |           |            |
         +            +------+    +            +------
                tw            tw           tw

When a trigger pulse is applied to the RTC or RTCN input, the output (QN) goes low for the duration of the pulse width (tw). After the pulse width time has elapsed, the output returns to its high state until the next trigger pulse is received.

Applications of the 4047 IC

The 4047 IC finds applications in various domains due to its versatility and ease of use. Some common applications include:

1. Timing Circuits: The 4047 IC can be used to generate precise timing pulses for controlling the duration of events or triggering actions in a system.

2. Pulse Generation: In monostable mode, the 4047 IC can generate single pulses with adjustable pulse widths, which can be used for triggering other circuits or devices.

3. Clock Signal Generation: In astable mode, the 4047 IC can generate a continuous square wave clock signal with a specific frequency, which can be used as a timing reference for synchronizing various parts of a system.

4. Frequency Division: By cascading multiple 4047 ICs in astable mode, you can create frequency divider circuits that generate lower frequency signals derived from a higher frequency input.

5. Pulse Width Modulation (PWM): The 4047 IC can be used to generate PWM signals by adjusting the duty cycle of the output square wave in astable mode. PWM signals find applications in motor speed control, LED dimming, and power regulation.

Practical Examples

Let’s explore a couple of practical examples that demonstrate the usage of the 4047 IC in both astable and monostable modes.

Example 1: Astable Mode – LED Blinking Circuit

In this example, we will use the 4047 IC in astable mode to create a simple LED blinking circuit. The circuit will make an LED blink at a specific frequency determined by the values of the external resistor and capacitor.

Components Required:
– 4047 IC
– LED
– Resistor (R)
– Capacitor (C)
– Breadboard
– Jumper wires

Circuit Diagram:

            +-----+
            |     |
            |     |
            |     |
        +---+     +---+
        |   4047 IC   |
        |             |
        |   1     14  |---VDD
  LED---|>--2     13  |
        |   3     12  |
        |   4     11  |---VDD (ASTABLE)
        |   5     10  |
        |   6      9  |---R
        |   7      8  |---C
        +---|-----|---+
            |     |
           GND   GND

Steps:
1. Connect pin 14 (VDD) of the 4047 IC to the positive power supply.
2. Connect pin 7 (GND) of the 4047 IC to the ground.
3. Connect pin 11 (ASTABLE) to VDD to configure the IC in astable mode.
4. Connect the resistor (R) between pin 9 and VDD.
5. Connect the capacitor (C) between pin 8 and GND.
6. Connect the anode of the LED to pin 2 (Q) of the 4047 IC.
7. Connect the cathode of the LED to ground through a current-limiting resistor.
8. Power on the circuit.

The LED will start blinking at a frequency determined by the values of R and C. Adjust these values to change the blinking rate according to your requirements.

Example 2: Monostable Mode – Push Button Pulse Generator

In this example, we will use the 4047 IC in monostable mode to create a push button pulse generator. When the push button is pressed, the circuit will generate a single pulse with a specific duration determined by the values of the external resistor and capacitor.

Components Required:
– 4047 IC
– Push button
– Resistor (R)
– Capacitor (C)
– Breadboard
– Jumper wires

Circuit Diagram:

            +-----+
            |     |
            |     |
            |     |
        +---+     +---+
        |   4047 IC   |
        |             |
        |   1     14  |---VDD
        |   2     13  |
        |   3     12  |
        |   4     11  |---GND (ASTABLE)
        |   5     10  |
        |   6      9  |---R
  PB----|>--7      8  |---C
        +---|-----|---+
            |     |
           GND   GND

Steps:
1. Connect pin 14 (VDD) of the 4047 IC to the positive power supply.
2. Connect pin 7 (GND) of the 4047 IC to the ground.
3. Connect pin 11 (ASTABLE) to GND to configure the IC in monostable mode.
4. Connect the resistor (R) between pin 9 and VDD.
5. Connect the capacitor (C) between pin 8 and GND.
6. Connect one terminal of the push button to pin 5 (RTC) of the 4047 IC.
7. Connect the other terminal of the push button to ground.
8. Power on the circuit.

When the push button is pressed, it triggers the 4047 IC, and a single pulse with a duration determined by R and C will be generated at pin 3 (QN) and pin 4 (QN). The pulse duration can be adjusted by changing the values of R and C.

Frequently Asked Questions (FAQ)

1. What is the difference between astable and monostable modes in the 4047 IC?
2. In astable mode, the 4047 IC continuously generates a square wave output without any external trigger. The frequency and duty cycle of the output are determined by the external resistor and capacitor values.

3. In monostable mode, the 4047 IC generates a single output pulse of a fixed duration in response to an external trigger signal. The pulse width is determined by the external resistor and capacitor values.

4. Can the 4047 IC be used with a microcontroller?

5. Yes, the 4047 IC can be interfaced with a microcontroller. The microcontroller can control the mode of operation (astable or monostable) by setting the appropriate logic level on the ASTABLE pin. Additionally, the microcontroller can read the output signals from the 4047 IC for further processing or triggering other actions.

6. How can I change the frequency of the output square wave in astable mode?

7. To change the frequency of the output square wave in astable mode, you need to adjust the values of the external resistor (R) and capacitor (C) connected to pins 8 and 9 of the 4047 IC. The frequency is inversely proportional to the product of R and C. Increasing the values of R and C will decrease the frequency, while decreasing the values will increase the frequency.

8. What is the maximum supply voltage that can be applied to the 4047 IC?

9. The 4047 IC can operate with a supply voltage ranging from 3V to 15V. It is important to ensure that the supply voltage does not exceed the maximum rating specified in the datasheet to avoid damaging the IC.

10. **Can multiple