Colpitts oscillator ampop

Thread Starter

beirao

Joined Feb 22, 2012
12
Hi,

I´m designing the colpitts oscillator in attachment. At first stight, the oscillator is stable, but the frequency oscillates over time; the oscillation is notorious in my aplication. Can you help me?

Thanks!

(sorry for my bad english)
 

Attachments

Thread Starter

beirao

Joined Feb 22, 2012
12
Hi,

My previous circuit is wrong. The C10 don´t connect the pin 2 of UA741 connect but the R11 and L1; but the circuit continues instable.
 

Thread Starter

beirao

Joined Feb 22, 2012
12
Thanks for your answer. Yes, I use the schematic of this website.

My inductor is the 5mH. In this case, my goal is vary the frequency by vary the inductor. I replace the capacitor of 10uF by 1uF but is instable too...
 

tshuck

Joined Oct 18, 2012
3,535
Thanks for your answer. Yes, I use the schematic of this website.

My inductor is the 5mH. In this case, my goal is vary the frequency by vary the inductor. I replace the capacitor of 10uF by 1uF but is instable too...
C10 is connecting to the inverting input of stage 1 when it should be connecting to the node R11 and L1 are sharing...
 

Thread Starter

beirao

Joined Feb 22, 2012
12
Hi,

I need a solution for vary a frequency by inductance variation. I use a colpitts oscillator because thought that was a stable oscillator. Any sugestion? :)
 

Thread Starter

beirao

Joined Feb 22, 2012
12
Thanks for your answer!

But your circuit is different of my... what is the better?

In this momment I have a oscillator to stable in a breadboard but in PCB is instable.. I think that is layout of my PCB is wrong in terms of GND, for example..
 

Ron H

Joined Apr 14, 2005
7,014
Thanks for your answer!

But your circuit is different of my... what is the better?

In this momment I have a oscillator to stable in a breadboard but in PCB is instable.. I think that is layout of my PCB is wrong in terms of GND, for example..
The circuit you posted won't work, partly because the op amp output is connected directly to one of the capacitors in the LC resonant circuit. My circuit works, at least in simulation.
 

Thread Starter

beirao

Joined Feb 22, 2012
12
The circuit you posted won't work, partly because the op amp output is connected directly to one of the capacitors in the LC resonant circuit. My circuit works, at least in simulation.
Thanks for your attention. In this momment my circuit too works :) How I saida, the problem is in PCB and is problem os stability; but I will test your circuit too!

Thanks!
 
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