1. Home
  2. Hobby Electronics Basics
  3. Calculating Input Noise Voltage

Calculating Input Noise Voltage

I was just checking out various opamp datasheets. I encountered this opamp:

formatting link

In the few lines of text, it says that the input noise voltage is 9 nV/ sqrt(Hz) at 10kHz. But in the table at the bottom of the page, it says that the input noise voltage is 18 nV/sqrt(Hz) at 1kHz.

How did they calculate this?

I'm curious because if I were to use an opamp (not necessarily this one) then I would like to know how much input noise voltage it contributes for a certain bandwidth, for instance audio band from 20Hz to 20kHz. There was another discussion that I saw (don't remember the link) that mentioned that at one particular design, the amplifier was designed with a 40dB gain and the input noise got amplified to about

100mV.
Reply to
MRW
Loading thread data ...

"MRW"

** Groper fool alert.

** See figure 19 ??

See how the EIN goes up dramatically at frequencies below 3 kHz ?

Go check some other op-amps - discover they are not all like that.

** Normally just multiply the typical or 1 kHz EIN figure by 141 (= sq rt 20,000)

....... Phil

Reply to
Phil Allison

Thanks, Phil! I'll take a look at other datasheets. Got any opamps you can recommend for audio?

Reply to
MRW

"MRW"

** See:

formatting link

...... Phil

Reply to
Phil Allison

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.