THS4500-EP Datasheet, PDF (25/38 Pages) National Semiconductor (TI) – WIDEBAND, LOW-DISTORTION, FULLY DIFFERENTIAL AMPLIFIER

THS4500-EP
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C_F
R_S
R_G
R_F
5V
V_S
R_T
5V
10 mF 0.1 mF _RISO
+_-
V_OCM
IN ADS5410
12-Bit/80 MSPS
1 mF
-+
THS4503
IN
R_ISO
CM
R_G
5 V ^{10 mF 0.1 mF}
R_F
0.1 mF
C_F
Figure 103. Using the THS4503 With the ADS5410
C_F
R_S
R_G
R_F
5V
V_S
R_T
5V
10 mF
+_-
V_OCM
0.1 mF
R_ISO
IN ^ADS5421
14-Bit/40 MSPS
-⁺
IN
CM
1 mF
THS4501
R_ISO
R_G
R_F
C_F
0.1 mF
Figure 104. Using the THS4501 With the ADS5421
FULLY DIFFERENTIAL LINE DRIVERS
The THS4500 family of amplifiers can be used as
high-frequency, high-swing differential line drivers.
The high power-supply voltage rating (16.5 V
absolute maximum) allows operation on a single 12-V
or a single 15-V supply. The high supply voltage,
coupled with the ability to provide differential outputs,
enables the ability to drive 26 V_PP into reasonably
heavy loads (250 Ω or greater). The circuit in
Figure 105 illustrates the THS4500 family of devices
used as high-speed line drivers. For line driver
applications, close attention must be paid to thermal
design constraints because of the typically high level
of power dissipation.
SLOS832 – JUNE 2013
R_S
C_{G RG}
R_F
15 V
V_S
R_T
R_ISO ^CS
V_OCM
+_-
THS4500/2
V_DD
R_L
0.1 mF
+
-
R_{ISO CS}
R_F
R_G
C_G
V_OD = 26 V_PP
Figure 105. Fully Differential Line Driver With
High Output Swing
FILTERING WITH FULLY DIFFERENTIAL
AMPLIFIERS
Similar to single-ended counterparts, fully differential
amplifiers have the ability to couple filtering
functionality with voltage gain. Numerous filter
topologies can be based on fully differential
amplifiers. Several of these are outlined in the
application report A Differential Circuit Collection
(literature number SLOA064), referenced at the end
of this data sheet. The circuit below depicts a simple,
two-pole, low-pass filter applicable to many different
types of systems. The first pole is set by the resistors
and capacitors in the feedback paths, and the second
pole is set by the isolation resistors and the capacitor
across the outputs of the isolation resistors.
C_F1
R_S
R_G1
R_F1
R_T
R_ISO
V_S
+
-
C VO
+
-
R_G2
R_ISO
R_F2
C_F2
Figure 106. A Two-Pole, Low-Pass Filter Design
Using a Fully Differential Amplifier With Poles
LocatedPa2t:=P(14_π=R(2_ISπ_OCR)F–C_1Fi)n^–1_Hinz Hz and
Often, filters like these are used to eliminate
broadband noise and out-of-band distortion products
in signal acquisition systems. It should be noted that
the increased load placed on the output of the
amplifier by the second low-pass filter has a
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