THS4551 Datasheet, PDF (47/70 Pages) Texas Instruments – Low-Noise, Precision, 150-MHz, Fully Differential Amplifier

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THS4551
SBOS778A – APRIL 2016 – REVISED AUGUST 2016
20
200
Gain (dB)
10
Phase (deg) 160
0
120
-10
80
-20
40
-30
0
-40
-40
-50
-80
-60
100k
1M
10M
Frequency (Hz)
100M
-120
D071
Figure 86. Gain and Phase Plot with a Differential Input Capacitor
10.2 Typical Applications
10.2.1 An MFB Filter Driving an ADC Application
One common application for the THS4551 is to take a single-ended, high V_PP voltage swing (from a high-voltage
precision amplifier such as the OPA192) and deliver that swing to precision SAR ADC as a single-ended to
differential conversion with output common-mode control and implement an active 2nd-order multiple feedback
(MFB) filter design. Designing for a 40-V_PP maximum input down to an 8-V_PP differential swing requires a gain of
0.2 V/V. Targeting a 100-kHz Butterworth response with the RC elements tilted towards low noise gives the
example design of Figure 87. Note that the V_CM control is set to half of a 4.096-V reference, which is typical for
5-V differential SAR applications.
OPA192 Output
RF1
592
THS4551 Wideband,
Fully Differential Amplifier
VS+
VS-
+
5V
±
0V ⁺
±
VIN
VOCM
+
2.048 V
±
2.96 k
1.5 nF
2.96 k
RG1
1.57 k
100 fF
RG2
1.57 k
910 pF
VOCM
VS+
±
+
FDA
±
+
PD
VS- ^VS+
RF2
592
910 pF
20
10
20
10
100 pF
2.2 nF
8-VPP Differential
SAR ADC Input
100 pF
Copyright © 2016, Texas Instruments Incorporated
Figure 87. Example 100-kHz Butterworth Filter
Copyright © 2016, Texas Instruments Incorporated
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