ADA4961ACPZN-R7 datasheet(16/25 Pages) AD

16 / 25 page

Data Sheet

ADA4961

AC CHARACTERIZATIONOUTPUT FILTER

Figure 37 is used in part of the accharacterization of the

ADA4961. The picosecond 5310 balun providesthe differential

input signal and the 100 Ω differential match to the device. The

3 dB pads make the picosecond balun 50 Ω impedance less

reactive on one side, which balances the differential phase

accuracy. On the outputs, the 2 nH and 2 pF create a two-pole

low-pass filter, along with the two 50 Ω resistors in parallel with

the pads and output picosecond balun.This filter createsthe

50 Ω differential load.

The output pads makethe load morebalanced. This is essential

for good HD2 performance. This filter techniquealso creates a

lighter load (slight peaking)for the device at higher frequencies,

which improvesthe IMD3 performance. Though the filter

bandwidth (BW)computes to 3.3 GHz, the parasiticC (not

shown in Figure 37) across the 2 nH filter inductors reducesthe

3 dB BW to about 2 GHz(see Figure 4). The filter, beyond

reducing integrated output noise, also reduces the higher

frequency second and third harmonics above1 GHzand

700 MHz, respectively (see Figure 20 and Figure 21).

Rev. A | Page 15 of 24

ADA4961ACPZN-R7 データシート(PDF) 16 Page - Analog Devices