@Audioguru again : I think you can answer my first question
Please look first image :
In normal common base colpitts : there is a capacitor from the emitter side to ground and from emitter to collector : here no emitter capacitor : in calculating frequency : the total capacitance in the image circuit will be (0-40) + 4.7 pf correct?
Can't understand it : use to think the emitter should be grounded or with little degeneration. Please someone explain everything : don't understand it
In the 2nd image : excluding the 0-25pf, the total capacitance is 43 in series with 140 correct? Used to think the 140pf was like a low pass filter but now guess it is part of the colpitts
If correct in the last sentence then the frequency is about 51Mhz but in the book it is meant to be 88-108 Mhz
What then is the use for the varactor diode in the last 2 images ? where should it be placed? at collector? why? what does it do?
Thanks thanks, thanks and................. Thanks
Also, some months ago : found an inductance meter on aliexpress than could measure down to nH (someone posted image on measuring air inductor) : now can afford it but can't find it anymore... Can someone asssist please?
Also, looking at the 3rd image : In any calculation , the 100 ohms and 1k are in parallel yeah?
Please look first image :
In normal common base colpitts : there is a capacitor from the emitter side to ground and from emitter to collector : here no emitter capacitor : in calculating frequency : the total capacitance in the image circuit will be (0-40) + 4.7 pf correct?
Can't understand it : use to think the emitter should be grounded or with little degeneration. Please someone explain everything : don't understand it
In the 2nd image : excluding the 0-25pf, the total capacitance is 43 in series with 140 correct? Used to think the 140pf was like a low pass filter but now guess it is part of the colpitts
If correct in the last sentence then the frequency is about 51Mhz but in the book it is meant to be 88-108 Mhz
What then is the use for the varactor diode in the last 2 images ? where should it be placed? at collector? why? what does it do?
Thanks thanks, thanks and................. Thanks
Also, some months ago : found an inductance meter on aliexpress than could measure down to nH (someone posted image on measuring air inductor) : now can afford it but can't find it anymore... Can someone asssist please?
Also, looking at the 3rd image : In any calculation , the 100 ohms and 1k are in parallel yeah?
Attachments
-
90.2 KB Views: 22
-
121.6 KB Views: 20
-
468.8 KB Views: 20