RF2461 datasheet(8/14 Pages) RFMD

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RF2461

Rev B6 DS060925

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.

L1, C1, and R form a current combiner which performs a differential to single-ended conversion at the IF frequency and sets

the output impedance. In most cases, the resonance frequency is independent of R and can be set according to the following

equation:

Where CEQ is the equivalent stray capacitance and capac-

itance looking into pins 11 and 12. An average value to

use for CEQ is 2.5pF to 3pF.

R can then be used to set the output impedance according to the following equation:

where ROUT is the desired output impedance and RP is the

parasitic equivalent parallel resistance of L1.

C1 should be chosen as high as possible (not greater

than 15pF), while maintaining an RP of L1 that allows for

the desired ROUT.

L2 and C2 serve dual purposes. L2 serves as an output

bias choke, and C2 serves as a series DC block.

In addition, L2 and C2 may be chosen to form an imped-

ance matching network if the input impedance of the IF

filter is not equal to ROUT. Otherwise, L2 is chosen to be

large, and C2 is chosen to be large if a DC path to ground

is present in the IF filter, or omitted if the filter is DC

blocked.

π L1

2 (C1 + CEQ)

fIF =

R =

4 ROUT

- 1

() -1

RF2461 Datasheet(PDF) 8 Page - RF Micro Devices