OPA836_15 Datasheet, PDF (38/57 Pages) Texas Instruments – OPAx836 Very-Low-Power, Rail-to-Rail Out, Negative-Rail In, Voltage-Feedback Operational Amplifiers

OPA836, OPA2836
SLOS712G – JANUARY 2011 – REVISED OCTOBER 2015
www.ti.com
9.2.1.3 Application Curves
A 10-Ω series resistor can be inserted between the capacitor and the noninverting pin to isolate the capacitance.
Figure 75 shows the THD+N performance with 100-kΩ and 300-Ω loads, with A-weighting and with no weighting.
Both loads show similar performance. With no weighting, the THD+N performance is dominated by the noise;
whereas A-weighting provides filtering that improves the noise.
Figure 76 and Figure 77 show FFT output with a 1-kHz tone and 100-kΩ and 300-Ω loads. To show relative
performance of the device versus the test set, one channel has the OPA836 device in line between generator
output and analyzer input and the other channel is in “Gen Mon” loopback mode, which internally connects the
signal generator to the analyzer input. With 100-kΩ load, Figure 76, the curves are basically indistinguishable
from each other except for noise, which means the OPA836 device cannot be directly measured. With 300-Ω
load, Figure 77, the main difference between the curves is the OPA836 device shows slightly higher even-order
harmonics, but odd order is masked by the test set performance.
-90
-95
-100
-105
-110
-115
No weighting
R_L = 300 W,
R_L = 100 kW
A-weighting
R_L = 300 W,
R_L = 100 kW
V_S = 5 V,
V_OUT = 1 V_RMS,
G = 1,
R_F = 0 W,
BW = 80 kHz
-120
10
100
1k
10k
f - Frequency - Hz
100k
Figure 75. OPA836 1 V_RMS 20-Hz to 80-kHz THD+N
0
-10
V_S = 5 V,
-20
V_OUT = 1 V_RMS,
G = 1,
-30
R_F = 0 W
-40
-50
-60
-70
-80
-90
-100
-110
Gen Mon - 100k
-120
-130
R_L = 100k
-140
0
2k 4k 6k 8k 10k 12k 14 16k 18k 20k
f - Frequency - Hz
Figure 76. OPA836 and AP Gen Mon 10-kHz FFT Plot; V_OUT
= 1 V_RMS, R_L = 100 kΩ
0
-10
V_S = 5 V,
V_OUT = 1 V_RMS,
-20
G = 1,
-30
R_F = 0 W
-40
-50
-60
-70
-80
-90
-100
Gen Mon - 300
-110
-120
R_L = 300
-130
-140
0
2k 4k 6k 8k 10k 12k 14 16k 18k 20k
f - Frequency - Hz
Figure 77. OPA836 and AP Gen Mon 10-kHz FFT Plot;
V_OUT = 1 V_RMS, R_L = 300 Ω
38
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