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Design >> Analog Design >> Varactor-R LPF
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Message started by eng on May 21^st, 2007, 12:12pm

Title: Varactor-R LPF
Post by eng on May 21^st, 2007, 12:12pm

Hi all,
Attached figure shows a basic tunable integrator which will be used in a LPF with couple hundred kHz cutoff freq. The process supplies 2 port varactor devices so two back-to-back varactors are needed around OTA in order not to disturb DC op points while tuning. Then in this case node A is low impedance node which disturbs AC response. Does a 30k resistor between node A and Vtune fix that problem?
I need your comments on this kind of integrator with varactors? The bottlenecks & ways to improve it etc.

thanks
eng,