varicap fm

Hi guys,

Any sugestion for a varicap that can be use for the entire FM radio band. I have tried some but none of them can cover the entire range. It would be nice if Vtune is less than 3 v. Thank you

Hi,

Search for some schematics designs over the web or look at these links :

h**p://hem.passagen.se/communication/fm_500.html

h**p://hem.passagen.se/communication/fm_pll_vco.html

h**p://www.semiconductors.philips.com/markets/mms/products/discretes/featured_products/rf_varicaps/

h**p://www.semiconductors.philips.com/acrobat_download/other/discretes/philips_rf_manual_6th_edition.pdf

Replace * by t

Suitable diodes have about 35 to 40pF at 3V and capacitance ratio about 2.5. Such diodes are BB204 (double, 30V), BB914 (double, 8V), KV1561 (single), KV1310(double, 8V), KV2201, KV2202, KV2204, MV209, MV2111, MV104.....

Hi

If u want a 3V varicapdiode then choose BB202 from Philips.
See their website...
This is much more modern diode as the old ones intended for 8V and 30V.
Commercially available FM recvrs such as the TEA57xx family do use them.

rgds

Mike