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| OPA2211-EP_16 Datasheet, PDF (19/32 Pages) Texas Instruments – Low-Power, Precision Operational Amplifier | |||
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8.2 Typical Application
Noise in Noninverting Gain Configuration
R2
R1
EO
RS
VS
OPA2211-EP
SBOS761 â NOVEMBER 2015
Noise at the output:
2
2
EO2 =
1+
R2
R1
en2 + e12 + e22 + (inR2)2 + eS2 + (inRS)2
1+
R2
R1
Where eS = Ã4kTRS ´
1+
R2
R1
= thermal noise of RS
e1 = Ã4kTR1 ´
R2
R1
= thermal noise of R1
e2 = Ã4kTR2 = thermal noise of R2
Noise in Inverting Gain Configuration
R2
R1
RS
EO
VS
Noise at the output:
2
EO2 =
1 + R2
R1 + RS
en2 + e12 + e22 + (inR2)2 + eS2
Where eS = Ã4kTRS ´
R2
R1 + RS
= thermal noise of RS
e1 = Ã4kTR1 ´
R2
R1 + RS
= thermal noise of R1
e2 = Ã4kTR2 = thermal noise of R2
For the OPA211 series op amps at 1kHz, en = 1.1nV/ÃHz and in = 1.7pA/ÃHz.
Figure 41. Noise Calculation in Gain Configurations
R1
R2
Signal Gain = 1+ R2
R1
Distortion Gain = 1+ R2
R1 II R3
R3
OPA2211-EP
VOUT
Generator
Output
Analyzer
Input
SIG. DIST.
GAIN GAIN R1
1 101 ¥
R2
R3
1kW 10W
11 101 100W 1kW 11W
Audio Precision
System Two(1)
with PC Controller
Load
(1) For measurement bandwidth, see Figure 43, Figure 44, and Figure 45.
Figure 42. Distortion Test Circuit
Copyright © 2015, Texas Instruments Incorporated
Product Folder Links: OPA2211-EP
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