Hi everyone. I have some questions about the CC colpitts oscillator.
Most books say the CC oscillator is very rare to use, and the cc
configuration is usually used for impeadance matching(high in- low out)
or buffer amplifier.But I find that some uhf PNP transistor is designed for CC oscillator.(and the datasheet emphasizes the the term "for common collector")
What is the purpose to use common collector configuration rather the
common emitter configuration?
Anyone knows the basic diagram for CC colpitts oscillator?

 

Hi,

Common collector transistors have gains of less than unity. Oscillators have to have gains graeter than unity in order to oscillate. So a common collector colpitts oscillator seems more trouble than it is worth.

Got a number for that UHF PNP transistor?

 

newman123,

I don't know if this will help but here is a link to a CC Colpitts Oscillator Analysis.

hgmjr

 

Microchip has a very good application note on oscillators: AN826

Crystal Oscillator Basics and Crystal Selection​

for rfPICTM and PICmicro® Devices