### Author Topic: LM324 Based Function Generator  (Read 2918 times)

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#### johnnyblaz

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##### LM324 Based Function Generator
« on: April 25, 2017, 07:42:36 pm »
Hi There!
I'm trying to make a function Generator using LM324 but the output is not as desired. When I change the resistor and capacitor values, I get a straight line at the output. I added a 2 pole RC Filter to get the triangle and sine waves but I need to change the frequency and amplitude of the Triangle wave to 5 khz, 5 Volt and the sine wave to 50Hz, 5 volt. How do I change it........ Kindly help.
Thanks

#### Mechatrommer

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• reassessing directives...
##### Re: LM324 Based Function Generator
« Reply #1 on: April 25, 2017, 11:45:00 pm »
where is the circuit?
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?

#### Kleinstein

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##### Re: LM324 Based Function Generator
« Reply #2 on: April 26, 2017, 04:08:54 pm »
The trinagle wave part is about normal for a ver low cost, low frequency version. However the way to make a sine from the triangle will not work this way - at best it is frequency dependent, as it is only an integrator applied to the sine. So the amplitude of the waveform will be invers proportional to frequency.

Usually function generators us a nonlinear but frequency independent circuit to make a sine like waveform. This could be something like an 2 transistor difference amplifier driven to partial saturation. Another option is a chain of diodes to make a kind of part wise linear circuit.

The LM324 may show a lot of take over distortion, so it may result in a poor waveform.

#### PCB.Wiz

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##### Re: LM324 Based Function Generator
« Reply #3 on: May 02, 2017, 09:59:44 am »
Hi There!
I'm trying to make a function Generator using LM324 but the output is not as desired. When I change the resistor and capacitor values, I get a straight line at the output. I added a 2 pole RC Filter to get the triangle and sine waves but I need to change the frequency and amplitude of the Triangle wave to 5 khz, 5 Volt and the sine wave to 50Hz, 5 volt. How do I change it........ Kindly help.
If you have 5KHz and need 50Hz, that's 100x lower, so just multiply the timing resistors by 100.
What exactly are you wanting to use this for ? What stability and accuracy do you need ?
LM324 is close to the worst OpAmp out there, and most 100nF caps will have poor precision and drift.

#### hugo

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##### Re: LM324 Based Function Generator
« Reply #4 on: May 05, 2017, 11:20:35 pm »

Smf