Overall Summary: The BB212 Varicap Diode from Philips is a dual version of the BB112 in the same TO92 package and is electrically similar to the MVAM108 series from Motorola. It has a very high capacitance ratio and extremely good linear tuning potential. It was intended for AM (medium wave) radio tuners but is now becoming obsolete. (I am looking for other versions now). An alternative design approach is to use a VHF Varicap (e.g. BB153) operating at 4 or 8 times the operating frequency and dividing down with HC7474 Dual D Latches.
|The diode capacitance Cd = 600 pF at VR = 0.5 V. At an operating frequency of FRF = 3.7 MHz, its series resistance rs < 1.5 Ohms suggests a worst case Q > 47.8.|
|This Q value may appear low but it has little degradation on overall VCO resonator Q as it will be lightly coupled to achieve a tuning range ratio much less than its capability available from its high capacitance range ration of 18 (1V < VR < 8.5 V).|
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