THS4504 Datasheet, PDF (23/45 Pages) National Semiconductor (TI) – WIDEBAND, LOW-DISTORTION, FULLY DIFFERENTIAL AMPLIFIERS

THS4504
THS4505
www.ti.com ......................................................................................................................................................... SLOS363D – AUGUST 2002 – REVISED MAY 2008
EXAMPLE ANALOG-TO-DIGITAL
CONVERTER DRIVER CIRCUITS
The THS4500 family of devices is designed to drive
high-performance ADCs with extremely high linearity,
allowing for the maximum effective number of bits at
the output of the data converter. Two representative
circuits shown below highlight single-supply operation
and split supply operation. Specific feedback resistor,
gain resistor, and feedback capacitor values are not
specified, as their values depend on the frequency of
interest. Information on calculating these values can
be found in the applications material above.
C_F
R_S
R_G
R_F
5V
V_S
R_T
5V
10 mF
+_-
V_OCM
0.1 mF
R_ISO
IN _ADS5410
12-Bit/80 MSPS
-+
IN
CM
1 mF
THS4503
R_ISO
R_G
5 V ^{10 mF 0.1 mF}
R_F
0.1 mF
C_F
Figure 79. 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 80. Using the THS4501 with the ADS5421
Figure 81 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 due to the typically high level of
power dissipation.
R_S
C_{G RG}
R_F
V_S
R_T
15 V
R_ISO ^CS
V_OCM
+_-
THS4504
V_DD
R_L
0.1 mF
-⁺
R_{ISO CS}
R_F
R_G
C_G
V_OD = 26 V_PP
Figure 81. Fully Differential Line Driver with High
Output Swing
FILTERING WITH FULLY DIFFERENTIAL
AMPLIFIERS
Similar to their 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 A
Differential Circuit Collection (SLOA064), referenced
at the end of this data sheet. The circuit in Figure 82
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
FULLY DIFFERENTIAL LINE DRIVERS
The THS4500 family of amplifiers can be used as
high-frequency, high-swing differential line drivers.
Their 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
C_F2
Figure 82. A Two-Pole, Low-Pass Filter Design
Using a Fully Differential Amplifier with Poles
LocatedPa2t=P(14_×=R(2_IS×_ORC_{F)C–1Fi)n}^–1_Hinz Hz and
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