what value of RF choke should i use on my clapp oscillator at 635Khz

[jackammo]

what value of RF choke should i use on my clapp oscillator at 635Khz

 

[goldsmith]

Dear jackammo
Hi
What kind of clapp oscillator you are referring to ? can you show me the schematic , please ?
By the way , is out put impedance important for you ?
Best Wishes
Goldsmith

 

[vfone]

If you are referring to the Clapp oscillator similar to the one in the link bellow (Fig 18-8), the RFC reactance should be about 10x higher than the load impedance, which usually is 50 ohms. So, the RFC should be 500 ohms at 635kHz, which is about 125uH.

https://wps.prenhall.com/chet_paynter_introduct_6/0,5779,426330-,00.html

 

[jackammo]

yes sir,, but how about the value for the resistors and capacitors.
the output should be 635Khz with a minimum of 5Vpk-pk.
transistor hfe=300, Vcc=12v.. could you help how to compute for the values.. thanks

.........

 

[goldsmith]

Hi jackammo
I think you want know how to design an oscillator , right ? if yes , what kind of way your are interested to learn ? we have three ways ! a first one is completely mathematical . and the second way is with some math and some softwares and the other one is mizture between math and some experiences . i'm using this way . and i have designed maximum frequency of 850 MHZ with this way , and vout = 35 volts ( 70 volts P-P ) . if you are interested i can help you at this way .
Best Wishes
Goldsmith

 

[jackammo]

the mathematical part sir

 

[goldsmith]

Hi again
Are you referring to something like this ?

If yes it is enough that AV* Beta be a bit greater than one thus you can be sure that your circuit will have stable oscillations . it is the rule for all of the feedback oscillators entire of this world ! so you should try to set your circuit with that specification .
Best Wishes
Goldsmith