malolo
Junior Member level 1
Hi all,
I'm wondering if anyone could clear some issues i have on op-amp output noise.
Seems total output noise would have a KT/C form (with coefficient), and C is the load cap. therefore, a general rule to reduce total output noise is to use large loading cap.
however, from textbook, if we dont take load cap into consideration, the derived equation for output noise spectral density would have a 4kt*2/3*[1/gm1 + gm2/gm1^2] sorta form and concludes that input transistor better have a large gm to reduce output noise.
Seems any op-amp would inevitably have load cap, then in what way would transconductance gm be incoporated in op-amp design ( especially for use in ADC)?
Any comments are appreciated! thanks!
Kev
I'm wondering if anyone could clear some issues i have on op-amp output noise.
Seems total output noise would have a KT/C form (with coefficient), and C is the load cap. therefore, a general rule to reduce total output noise is to use large loading cap.
however, from textbook, if we dont take load cap into consideration, the derived equation for output noise spectral density would have a 4kt*2/3*[1/gm1 + gm2/gm1^2] sorta form and concludes that input transistor better have a large gm to reduce output noise.
Seems any op-amp would inevitably have load cap, then in what way would transconductance gm be incoporated in op-amp design ( especially for use in ADC)?
Any comments are appreciated! thanks!
Kev
