THS4531A Datasheet, PDF (32/50 Pages) Texas Instruments – Ultra Low Power, Rail-to-Rail Output, Fully-Differential Amplifier

THS4531A
SLOS823A – DECEMBER 2012 – REVISED JANUARY 2013
200
100
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10
V_S = 2.7 V
G = 1 V/V
R_F = 2 kΩ
R_L = 2 kΩ
1
1
10
100
1k 2k
C_LOAD (pF)
G068
Figure 80. Recommended Series Output Resistor vs Capacitive Load for Flat Frequency Response
3
0
−3
−6
−9
−12
−15
−18
−21
100k
V_S = 2.7 V
G = 1 V/V
R_F = 2 kΩ
R_L = 2 kΩ
V_OUT = 100 mV_pp
C_L = 0 pF, R_O = 0 Ω
C_L = 15 pF, R_O = 200 Ω
C_L = 39 pF, R_O = 100 Ω
C_L = 120 pF, R_O = 50 Ω
C_L = 470 pF, R_O = 20 Ω
C_L = 1200 pF, R_O = 12 Ω
1M
10M
Frequency (Hz)
100M
G069
Figure 81. Frequency Response for Various R_O and C_L Values
Audio Performance
The THS4531A provides excellent audio performance with very low quiescent power. To show performance in
the audio band, the device was tested with an audio analyzer. THD+N and FFT tests were run at 1Vrms output
voltage. Performance is the same on both 2.7V and 5V supply. Figure 82 is the test circuit used, and Figure 83
and Figure 84 show performance of the analyzer. In the FFT plot the harmonic spurs are at the testing limit of the
analyzer, which means the THS4531A is actually much better than can be directly measured. Because the
THS4531A distortion performance cannot be directly measured in the audio band it is estimated from
measurement in high noise gain configuration correlated with simulation.
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