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Design >> Analog Design >> how to reduce the current sinker's noise
https://designers-guide.org/forum/YaBB.pl?num=1192024534

Message started by Robert on Oct 10^th, 2007, 6:55am

Title: how to reduce the current sinker's noise
Post by Robert on Oct 10^th, 2007, 6:55am

hi,all
i am designing a 2.5Gbps Transimpedance Amplifier currently, i utilize the cascode topology, the input impedance is greatly reduce to 1/gm, so the input pole is moved far away, however, i found the current sinker contributes large noise current to the input node directly, i have try to increase the Vgs(of course, i still make sure that it is in saturation) and minimize the W/L for a required current, but it still produces near 50% of total input rms referenced noise current. what methodes or techniques you guys would take to reduce its noise based on your experiencement, please let me know, i would really appreciate it, thanks a lot!

best Regards
Nio Lin

Title: Re: how to reduce the current sinker's noise
Post by loose-electron on Oct 13^th, 2007, 1:21pm

As a general rule, any and all current sources are big noise sources.

Consider a differenet topology, suggest getting rid of the current sources in favor of resistors (if applicable, dont know your circuits)

post the schematic for people to make better informed suggestions

jerry

Title: Re: how to reduce the current sinker's noise
Post by Robert on Oct 14^th, 2007, 7:22pm

Dear Jerry,
thanks for your reply!
the prototype i used is illustrated as attachment, currently i used the 0.35u CMOS process to design 2.5G/ 4G TIA, except the shunt-shunt feedback structure with cascode (regulated) as input stage, i do not have other solution.

Nio Lin