On Wed, Apr 2, 2025 at 03:34 PM, Brian Beezley wrote:
One thing I don't understand. Manufacturers specify useful frequencies several
times the capacitor self-resonant frequency, as revealed by the .s2p files
they supply. The 33 pF shown departs from 33 pF as it approaches its 1.6 GHz
SRF, which is nowhere near the 10 GHz specified upper frequency limit. All the
capacitor manufacturers seems to do this. Why?
This is common practice in microwave power amplifiers and and some MMIC designs
as one component brings in two. The R and L for above SRF of the C serves as a DC block
while adding a stabilizing R and an L for the match. The same tactic is used with distributive L.
First glance at some PA designs will most likely not make sense without recognizing that the parasitic is
used to advantage. A complete sim is required adding in all device models including the passives.
