Pulse Width Modulation (PWM) generator circuit using 741 op amp comparator with output wave form

Pulse width modulation (PWM) is a method of changing the duration of a pulse with respect to the analog input. The duty cycle of a square wave is modulated to encode a specific analog signal level. This pulse width modulation tutorial gives you the basic principle of generation of a PWM signal. The PWM signal is digital because at any given instant of time, the full DC supply is either ON or OFF completely.PWM method is commonly used for speed controlling of fans, motors, lights in varying intensities, pulse width modulation controller etc. These signals may also be used for approximate time-varying of analogue signals. Below you can see the pulse width modulation generator circuit diagram (pulse width modulator) using op amp. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Pulse width modulation dc motor control is one of the popular circuits in Robotics.

Circuit diagram

Opamp PWM circuit

Components required

  1. Dual power supply (+Vcc and -Vcc)
  2. 741 op amp IC
  3. Signal generator

Working of Pulse width modulator

  • It compares both the input voltages, i.e. the sawtooth waveform and the message signal (sine wave).
  • The duration for which the instantaneous value of sine wave is above that of sawtooth, op amp switches to +Vcc since the sine wave input is connected to the non inverting input of the op amp.
  • Also when the value of sine wave is less than the instantaneous value of sawtooth, op amp switches to -Vcc.
  • Thus we get a pulse waveform that swings between +Vcc and –Vcc.
  • That is the pulse width changes according to the message signal (Width of the pulse is modulated)

Output wave form

PWM Waveform

Important terms associated with PWM:

Period (T)
How long each complete pulse cycle takes.
Frequency (F)
How often the pulses are generated. This value is typically specified in Hz (cycles per second).

Duty Cycle (D)
Refers to the amount of time in the period that the pulse is active or high. Duty Cycle is typically specified as a percentage of the full period.


Components pin out

Opamp 741 pinout

6 thoughts on “Pulse Width Modulation (PWM) generator circuit using 741 op amp comparator with output wave form

  1. I want to create pwm waves using ua741,.as a comparator. if i give sine wave 5v/50hz to non inverting side & saw tooth waves to inverting side 5v /10khz. MY query is it will work practically in high frequency”S. If not which comparator ic shold i use.

  2. if i want to use two Function Generator ICs one for Triangular/sawtooth & the other for sine wave generation,instead of an Real Function Generator Equipment,then how should i supply these Function Generator ICs with caution of that the power supply has middle property?should i connect the negatives and positives sides of Function generators parallel together (Negative to Negative & Positive to positive)and then connect the positives to +Vcc and negatives to -Vcc?or i must connect the positives & negatives Of each Function Generator separately with different supply voltages?

    • i must notice that the function generators i am uses are XR2206 ICs,please tell me that How Should i Combine them With One 741 Op-Amp IC as you explained Above on that schematic?

  3. Hello dear Erfan, for function generator ICs i suggest 8038 and i work with it and its have good performance. For producing PWM although you can use 741 but its not a comparator and its a Op-Amp and if freq. become high the PWM go fail so i suggest LM339 comparator. Good Luck

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