Function gnerator

  • Thread starter abdo375
  • Start date
133
0
I'm trying to build a function generator that will output a sine, ramp and rect wave and I need to change the amplitude and the frequency of the signal, as far as the first part goes, I've succeeded, but I can't seem to control the frequency and the amplitude of the signal independently.
 
Last edited:
1,442
3
And you can't. You need to design an addition variable gain amplifier that will automatically compensate for an amplitude drop or gain. It's sometimes refered to as ALC, Automatic Level Control. That will level your amlitude through out your frequency range.
 

berkeman

Mentor
54,486
4,819
I'm missing something. Where does the sine wave pop out?
 

Averagesupernova

Science Advisor
Gold Member
3,472
479
Glad to see I'm not the only one who missed it Mike.
 
133
0
I'm sorry should have made it more clear, it pops from the integrator circuit (the output of the third Op-Amp) and the rect wave from the differentiator circuit(last one).
 

berkeman

Mentor
54,486
4,819
No, the integral of a triangle wave is not a sine wave. There is a different technique that is generally used for cheap tri --> sine conversion.
 
133
0
:confused: The output of the Integrator: http://img369.imageshack.us/img369/5135/labprojectschematic112ka0.jpg" [Broken]
cheap trick ???
 
Last edited by a moderator:

berkeman

Mentor
54,486
4,819
Hmmm. Well I don't get that. Does it make that sine-wave-looking waveform at only one frequency? Certainly a damped integration of a triangle wave is not a sine wave in general.

The cheap trick that I referred to is to use diodes and resistors to make an amplitude-dependent impedance that shapes the triangle into a sine. There used to be an IC with that inside it, but I forget the number.
 
133
0
I see your point berkemen (I'm surprised I haven't before) , I'm gonna look deeper into this.


too bad I can only use op-amps in the circuit, no IC's.
 
Last edited:

Want to reply to this thread?

"Function gnerator" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top