(A) Noise in Noninverting Gain Configuration

+

±

R2

R1

RS

+

±

VS

GND

Source

EO

GND

+

±

R2

R1

GND

EO

RS

+

±

VS

GND

Source

(B) Noise in Inverting Gain Configuration

:1; '

1 =

l1+42

41

p„¨:A

5

;2 +:A

0

;2 +

kA

41æ42

o2+:E

0

„ 45

;2 +

lE

0

„

d41„42

41 + 42

hp2 >8

4/5

?

:2; A

5 =

¥4„G$„6(-)„45 d 8

¾*V

h

:3; A

41æ42 =

¨4„G

$

„ 6(-) „

d41„42

41 + 42

h d 8

¾*V

h

:4; G

$ = 1.38065

„ 10

F23

d ,

-

h

:5; 6(-) = 237.15+6(°%) >-?

Noise at the output is given as EO, where

Noise at the output is given as EO, where

:6; '

1 =

l1+ 42

45 + 41

p„¨:A

0

;2 +

kA

41+45 æ42

o2+FE

0

„

H:45 +41;„42

45 + 41 + 42 IG

2

>8

4/5

?

:7; A

41+45 æ42 =

¨4„G

$

„ 6(-) „

H:45 +41;„42

45 + 41 + 42 I

d 8

¾*V

h

:8; G

$ = 1.38065

„ 10

F23

d ,

-

h

:9; 6(-) = 237.15+6(°%) >-?

Thermal noise of RS

Thermal noise of R1 || R2

Boltzmann Constant

Temperature in kelvins

Boltzmann Constant

Temperature in kelvins

Thermal noise of (R1 + RS) || R2

Copyright © 2017, Texas Instruments Incorporated

Where en is the voltage noise spectral density of the amplifier. For the OPAx186 operational amplifier, en = 38 nV/√Hz at 1 kHz.

NOTE: For additional resources on noise calculations, visit TI Precision Labs.

Figure 8-1. Noise Calculation in Gain Configurations

OPA186, OPA2186, OPA4186

SBOS968C – JUNE 2022 – REVISED JULY 2023

www.ti.com

24

Submit Document Feedback

Copyright © 2023 Texas Instruments Incorporated

Product Folder Links: OPA186 OPA2186 OPA4186