[moved] Squarewave Generator using LM741

Status
Not open for further replies.

imranahmed

Advanced Member level 3
Joined
Dec 4, 2011
Messages
817
Helped
3
Reputation
6
Reaction score
3
Trophy points
1,298
Location
Karachi,Pakistan
Activity points
6,492
Please let me know that I built Squarewave generator using LM741 opamp but it

could not generate any output.

Please see attachment.
 

Attachments

  • SQWave.png
    31 KB · Views: 113

Re: Squarewave Generator using LM741

The 741's output cannot go lower than 2V above its low supply rail. Therefore the 741 needs a bipolar supply.

This relaxation oscillator will only work if the output goes down to 0V or into negative region. It may be sufficient if you make the lower supply rail -1 or -2V.
 
Last edited:
Try this modification.

- - - Updated - - -

If you want the output to switch down to zero, you can add a transistor like shown.
 

Attachments

  • 741.png
    22.5 KB · Views: 116
  • 741_1.png
    25 KB · Views: 124
Thank you E-design

I'll do this.

- - - Updated - - -

Dear bradtheRad,

I set low and high rail at +12 and -12
 

Make sure you are using an opamp model that can simulate. Some are only for schematic purposes and do not have a simulation model attached. It should work with your +12/-12 supply as you can see here.

- - - Updated - - -

Make sure there is an SPICE model attached.
 

Attachments

  • 741_2.png
    111.9 KB · Views: 108
  • 741_3.png
    5.6 KB · Views: 113
Thank you dear E-design, its working.

- - - Updated - - -

Dear E-design.

I want to generate 25kHz square wave but when I set C1=0.001uF and R1=18k-Ohms.

For example:

C1=0.001uF , R1=18k-Ohms

According to,
F=1/(2.2 * R1 * C1)

F = 25.2 kHz.

But it could not generate 25kHz pulses.
 

Attachments

  • SQWave.png
    29.4 KB · Views: 116

The lousy old 741 opamp design is 47 years old. It was designed for DC and low frequencies. Its datasheet shows that it has slew rate problems above 9kHz. Also, at 25kHz its voltage gain is fairly low.
To produce a half decent 25kHz squarewave it must produce the harmonics that are 250kHz and higher.
 

Dear Audioguru,

Please recommend me any opamp or IC to generate precise square wave.
 

Hi,

use a push-pull comparator.

like this:


Klaus
 
The older LF351 or a TL071 should work well for you.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…