I have a task to optimize noise in BW 10Hz - 10kHz.
Voltage gain shall be around 20..50. OA connected directly to source of signal,
which has impedance 1kOm DC and 50Om AC. OA connected to middle point of R1/R2 divider,
where R1 connected to OA (OUT), and R2 connected to GND.
1. For +5V supply we get not so many choice here - only OP284. (LM258 -noise not specified).
In AN-940 (attached) stated that it is optimized for 10kOm impedance,
which looks like too much for my case.
2. So, i have to use +5V&-5V supply. According AN-940, looks like best choise is somewhere between
AD797(450 Om - single OA per case -) AD8599 (550 Om + 2 OA per case +)
ADA4004-2(1.5 kOm + 2 OA per case +)) & ADA4075-2 (2.5 kOm - + 2 OA per case +)
3. Currently, i get acceptable result with AD8599 & R1=12.5 kOm, R2 = 500 Om.
But, if it is optimal in my case? Shall OA chain be optimized as well?
4. AD8599 consume 5mA per OA. So, tempting to use ADA4075-2, as it consume less and
2-3 times cheeper as far it is not precise (offset 2mV).
Please share your thinking.
Thanks in advance!