THS4522IPW datasheet(32/71 Pages) TI2

32 / 71 page

-95

101

103

105

107

109

111

113

115

100

1 k

10 k

100 k

Frequency (Hz)

TOTAL HARMONIC DISTORTION + NOISE

vs FREQUENCY (No Weighting)

100

110

120

130

140

5 k

10 k

15 k

20 k

25 k

30 k

35 k

Frequency (Hz)

Generator

THS4521

= 5.0 V

G = 1 V/V

R = 1 k

= 1 V

S+

OUT

RMS

10-kHz OUTPUT SPECTRUM

THS4521 on AP Analyzer

-50

100

110

120

Frequency (kHz)

TOTAL HARMONIC DISTORTION + NOISE

THS4521 Measured on AP Analyzer

THS4521

Signal Generator

THS4521, THS4522, THS4524

SBOS458H – DECEMBER 2008 – REVISED JUNE 2015

www.ti.com

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 method. The actual device

performance can be estimated by placing the device in a large noise gain and using the reduction in loop gain

correction. The THS4521 is placed in a noise gain of 101 by adding a 10-

Ω resistor directly across the input

terminals of the circuit shown in Figure 66. This test was performed using the AP instrument as both the signal

source and the analyzer. The second-order harmonic distortion at 1 kHz is estimated to be –122 dBc with VO =

1VRMS; third-order harmonic distortion is estimated to be –141 dBc. The third-order harmonic distortion result

matches exactly with design simulations, but the second-order harmonic distortion is about 10 dB worse. This

result is not unexpected because second-order harmonic distortion performance with a differential signal

depends heavily on cancellation as a result of the differential nature of the signal, which depends on board

layout, bypass capacitors, external cabling, and so forth. Note that the circuit of Figure 66 is also used to

measure crosstalk between channels.

The THS4521 shows even better THD+N performance when driving higher amplitude output, such as 5 VPP that

is more typical when driving an ADC. To show performance with an extended frequency range, higher gain, and

higher amplitude, the device was tested with 5 VPP up to 80 kHz with the AP. Figure 69 shows the resulting

THD+N graph with no weighting.

Figure 67. THS4521 1-VRMS 20-Hz to 20-kHz Thd+N

Figure 68. THS4521 1-VRMS 10-kHz FFT Plot

Figure 69. Thd+N (No Weighting) on Ap, 80-kHz Bandwidth at G = 1 With 5-VPP Output

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THS4522IPW Datasheet(PDF) 32 Page - Texas Instruments

THS4522IPW Datasheet(HTML) 32 Page - Texas Instruments

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