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Noise optimizing AD8599 &&

Question asked by Adex on Nov 6, 2015
Latest reply on Nov 17, 2015 by rvieja

Good day,

 

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!

 

BR

K

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