Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

triangle wave generator help

Status
Not open for further replies.

Michael Circuit

New Member
I am trying to build a triangle waveform generator using an lm 741 and this link **broken link removed** as a guide, all i am getting is a square wave out of each oscillator? any ideas?
 
Hello,

Many simple triangle generators are made by driving a near perfect integrator with a square wave. This one isnt that different in that it uses a comparator to get the square wave and an integrator to create a ramp that either ramps up or down.
Some problems that may come up are:
1. Not a high enough supply voltage to get the op amps to work correctly. You may have to turn the voltage up to 10 volts.
2. RC time constant for the integrator is not long enough.

You could check both of these to start with.
When the output of the first op amp changes state you should see the output from the second op amp start to ramp up or down, not just shoot up or down like a square wave would.
 
My guess is you're looking at the output of the wrong opamp. One will be a square wave and the other should be a triangle wave. The oscillator frequency will be determined by the RC value. What values are you using for R & C? Can you post a diagram of the circuit you built? Also, the 741 is only good for low frequency. What frequency are you trying to achieve?
 
using an lm741 i am able to generate a square wave. If the input to my second lm741 IC is a square wave the capacitor and grounded resistor in the second IC should turn the square wave into a triangle wave. by connecting a capacitor between the inverting input and the output and grounding the noninverting input I should be able to ramp down the output.which should make a triangle wave.. instead I get a wave form that looks like a square wave with a roof on it, it looks like a house on the oscilloscope, thats the best way to describe it, its a mix between a triangle wave and a square wave not what im aiming for. no matter what the R & C are i still get this bizzare looking waveshape
 
Last edited:
using an lm741 i am able to generate a square wave. If the input to my second lm741 IC is a square wave the capacitor and grounded resistor in the second IC should turn the square wave into a triangle wave. by connecting a capacitor between the inverting input and the output and grounding the noninverting input I should be able to ramp down the output.which should make a triangle wave.. instead I get a wave form that looks like a square wave with a roof on it, it looks like a house on the oscilloscope, thats the best way to describe it, its a mix between a triangle wave and a square wave not what im aiming for. no matter what the R & C are i still get this bizzare looking waveshape

Hi Michael,
This is a very simple function generator, based on a datasheet example.
I would recommend that you do not use 741 opa's on your projects, they are very old and have a very low specification.
 

Attachments

  • FunctGen3.gif
    FunctGen3.gif
    49.1 KB · Views: 2,680
using an lm741 i am able to generate a square wave. If the input to my second lm741 IC is a square wave the capacitor and grounded resistor in the second IC should turn the square wave into a triangle wave. by connecting a capacitor between the inverting input and the output and grounding the noninverting input I should be able to ramp down the output.which should make a triangle wave.. instead I get a wave form that looks like a square wave with a roof on it, it looks like a house on the oscilloscope, thats the best way to describe it, its a mix between a triangle wave and a square wave not what im aiming for. no matter what the R & C are i still get this bizzare looking waveshape

The non-inverting input to the triangle generator opamp is not connected to ground. It's connected to the vairable resistor, which creates a reference for the input. Connecting to ground won't work.
 
what op amps would you recommend instead of the 741?
This circuit uses two opamps so it should use a dual opamp.
The LM833 is a good dual opamp that works well up to 100kHz but its minimum supply voltage is 10V. It is low noise.
The MC34072 is also a good dual opamp that works well up to 100kHz. Its minimum supply voltage is only 3V. It is not low noise.
 
ericgibbs
what op amps would you recommend instead of the 741?

hi
I would suggest CA3240 dual OPA's, they cost less than 50pUK.
They work on single or dual supply voltages and IMO a low cost versatile OPA.
 
can anyone post schematics of other simple circuits they know will work? Ive been trying a bunch found online with little success.
for example
https://www.electro-tech-online.com/attachments/triangle-wave-oscillator-png.28722/
The circuit you posted works perfectly.
With a positive and negative 9V supply, its square-wave output is about 16V peak-to-peak into a 10k load to ground and its triangle-wave output is about 13V peak-to-peak into a 10k load to ground.
Its outputs can drive a load as low as 1k ohms but then its output levels might drop to half.
 
The circuit you posted works perfectly.
With a positive and negative 9V supply, its square-wave output is about 16V peak-to-peak into a 10k load to ground and its triangle-wave output is about 13V peak-to-peak into a 10k load to ground.
Its outputs can drive a load as low as 1k ohms but then its output levels might drop to half.

I should be able to apply this circuit to any dual op amp correct?
 
Last edited:
I should be able to apply this circuit to any dual op amp correct?
A lousy old LM358 dual opamp has a very poor high frequency response so if it is used in this circuit its square-wave and triangle-wave will have poor wave shapes.

A lousy old MC1458 dual opamp has two 43 years old lousy old 741 opamps.

There were many older opamps with poorer spec's.
 
point made, thank you. I am slowly but surely learning about op amps and wave generation using "lousy old" IC's because of they are very affordable = 25 cents each or so.
 
At Digikey today:
MC1458 lousy old dual 741 opamp $.65US each.
LM358 lousy old dual opamp $.46US each.
TL072 high quality audio dual opamp $.51US each.

One lousy old one costs much more than the excellent one! I selected the lowest cost manufacturers.
Why are you counting pennies? Pretty soon pennies will be obsolete.

EDIT: Not long ago you could get "a shave and a haircut, 2-bits."
2-bits is only 25 pennies. Today a shave and a haircut costs maybe $20.00 plus $3.00 for the tip.
 
Last edited:
This circuit still does not work properly, I can not generate any waveform using this schematic https://www.electro-tech-online.com/attachments/triangle-wave-oscillator-png.28722/. I fail to see how this is a comparator/integrator circuit. Shouldnt the inverting input of the comparator have a capacitor connected to ground to generator a square wave which would then slightly ramp down through the integrators inverting capacitor generating a triangle wave?
 
This circuit still does not work properly, I can not generate any waveform using this schematic. I fail to see how this is a comparator/integrator circuit. Shouldnt the inverting input of the comparator have a capacitor connected to ground to generator a square wave which would then slightly ramp down through the integrators inverting capacitor generating a triangle wave? on my oscilloscope there is a very clear upper trigger point, a huge jump.. but no triangle or square wave... just a jump,,, hhhmmmm this is quite frusterating.
 
This circuit still does not work properly, I can not generate any waveform using this schematic https://www.electro-tech-online.com/attachments/triangle-wave-oscillator-png.28722/. I fail to see how this is a comparator/integrator circuit. Shouldnt the inverting input of the comparator have a capacitor connected to ground to generator a square wave which would then slightly ramp down through the integrators inverting capacitor generating a triangle wave?

Why are you using a different User name from the original Michael Circuit and also a different ISP.???
Do you have two User names.????
 
it was easier to just make a new one, i couldnt remember my password or what e-mail account i used for the original. anyway I cant get this to work, ive tried so many combo's of a triangle wave oscillator my heads spinning... hhhmmm... could it be the dc power supply? i can get a square wave just fine.. triangle wave.. not even close.
 
Last edited:
it was easier to just make a new one, i couldnt remember my password or what e-mail account i used for the original. anyway I cant get this to work, ive tried so many combo's of a triangle wave oscillator my heads spinning... hhhmmm... could it be the dc power supply? i can get a square wave just fine.. triangle wave.. not even close.

OK,
What supplies are you using for the OPA's.?
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top