THS4521 Datasheet, PDF (29/43 Pages) Texas Instruments – VERY LOW POWER, NEGATIVE RAIL INPUT, RAIL-TO-RAIL OUTPUT, FULLY DIFFERENTIAL AMPLIFIER

THS4521
THS4522
THS4524
www.ti.com.................................................................................................................................................... SBOS458B – DECEMBER 2008 – REVISED MAY 2009
Audio Performance
The THS4521, THS4522, and THS4524 family
provide excellent audio performance with very low
quiescent power. To show performance in the audio
band, the device was tested with a SYS-2722 audio
analyzer from Audio Precision. THD+N and FFT tests
were performed at 1-V_RMS output voltage.
Performance is the same on both 3.3-V and 5-V
supplies. Figure 68 shows the test circuit used;
Figure 69 and Figure 70 show the performance of the
analyzer using internal loopback mode (generator)
together with the THS4521. Note that the harmonic
distortion performance is very close to the same with
and without the device meaning the THS4521
performance is actually much better than can be
directly measured by this meathod. Using these
measurements and simuation, we estimate the
second-order harmonic distortion to be –133 dBc and
the third-order harmonic distortion to be –140 dBc at
10 kHz. Note that the circuit of Figure 68 is also used
to measure crosstalk between channels on the
THS4522 and THS4524 using the crosstalk meter
function of the AP audio analyzer.
V_IN+
From
AP
Analyzer
V_{IN- Open}
1 kW
PD
0.22 mF
1 kW
1 kW
V_S+
THS452x
V_OCM
V_S-
1 kW
24.9 W
24.9 W
V_OUT-
V_OUT+ To AP
Analyzer
Open
0.22 mF
Figure 68. THS4521 AP Analyzer Test Circuit
-50
-60
-70
-80
-90
-100
-110
-120
0
TOTAL HARMONIC DISTORTION + NOISE
THS4521 Measured on AP Analyzer
THS4521
Signal Generator
5
10
15
20
Frequency (kHz)
Figure 69. THS4521 1-V_RMS 20-Hz to 20-kHz
THD+N
10-kHz OUTPUT SPECTRUM
THS4521 on AP Analyzer
10
0 ^VS+ ^{= 5.0 V}
-10 ^{G = 1 V/V}
-20 ^RF ^{= 1 kW}
-30 V_OUT = 1 V_RMS
-40
Generator
THS4521
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
0
5 k 10 k 15 k 20 k 25 k 30 k 35 k
Frequency (Hz)
Figure 70. THS4521 1-V_RMS 10-kHz FFT Plot
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Product Folder Link(s): THS4521 THS4522 THS4524