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| OPA211_08 Datasheet, PDF (16/17 Pages) Texas Instruments – 1.1nV/√Hz Noise, Low Power, Precision Operational Amplifier in Small DFN-8 Package | |||
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OPA211
OPA2211
SBOS377D â OCTOBER 2006 â REVISED FEBRUARY 2008
Noise in Noninverting Gain Configuration
R2
R1
EO
RS
VS
www.ti.com
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
OPA211
VO = 3VRMS
Generator
Output
Analyzer
Input
Audio Precision
System Two(1)
with PC Controller
RL
600W
SIG. DIST.
GAIN GAIN R1 R2 R3
1 101 ¥ 1kW 10W
11 101 100W 1kW 11W
NOTE: (1) Measurement BW = 80kHz.
Figure 42. Distortion Test Circuit
16
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Product Folder Link(s): OPA211 OPA2211
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