Problem with oscillation in 200kHz Colpitts oscillator

[MMachado]

Hi, i try to do a colpitts oscillator, with 200khz oscillation. I do the Schematics but i have problems to take the oscillation. i try to variate the resistance but nothing happen. what i can i do?

 

[E-design]

Re: colpitts oscilator

Re-check your values.

 

[MMachado]

Re: colpitts oscilator

I Re-check my values, and i dont fine what is wrong. i need help please.

Added after 1 minutes:

I go to try again thanks

 

[E-design]

Re: colpitts oscilator

10pF on the base of your cct is very low.

 

[vfone]

Re: colpitts oscilator

Just replace the Cb 10pf with a 10nF and it will start oscillate.

 

[MMachado]

Re: colpitts oscilator

I place the 10nF and start oscillate, thanks. but the sinusoid is not perfect. what can i do? I have the 200khz, but how can i get a perfect oscillacion?

Merry Christmas.

 

[MMachado]

Re: colpitts oscilator

colpitts oscilator with my values

 

[E-design]

Re: colpitts oscilator

What do you mean by perfect oscillation? Nothing is perfect. You can reduce the harmonics but not eliminate it.

 

[karesz]

colpitts oscilator

Hi,
You can select higher L/C (=higher Q) or apply
a tuned second stage >> has "cleaner" signal...
K.

 

[MMachado]

Re: colpitts oscilator

I want reduce the harmonics, how can i do that?

 

[vfone]

Re: colpitts oscilator

Place a Low Pass Filter at the output.