Datasheet
POWER-SUPPLY DECOUPLING
_
+
4
5
3
7
2
6
V
OCM
V
S
PwrPad
V
S
PD
1
8
R0805
R4
C4
C0805
R5
R0805
C3
C0805
R6
R7
R0805
R0805
C5
C6
C0805
C0805
C7
C0805
J2
J3
J2
J3
R2
R0805
R3
R0805
C1
C0805
C2
C0805
R1
R1206
J1
3
1
4
5
6
R11
R1206
R9
R0805
R8
R9
R0805
R0805
J2
J3
J4
T1
U1
THS450X
EVALUATION FIXTURES, SPICE MODELS,
THS4504
THS4505
www.ti.com
......................................................................................................................................................... SLOS363D – AUGUST 2002 – REVISED MAY 2008
TECHNIQUES AND RECOMMENDATIONS
Power-supply decoupling is a critical aspect of any
high-performance amplifier design process. Careful
decoupling provides higher quality ac performance
(most notably improved distortion performance). The
following guidelines ensure the highest level of
performance.
1. Place decoupling capacitors as close to the
power-supply inputs as possible, with the goal of
minimizing the inductance of the path from
ground to the power supply.
2. Placement priority should be as follows: smaller
capacitors should be closer to the device.
3. Use of solid power and ground planes is
recommended to reduce the inductance along
power-supply return current paths.
Figure 93. Simplified Schematic of the Evaluation
4. Recommended values for power supply Board. Power-Supply Decoupling, V
OCM
, and
Power-Down Circuitry not Shown
decoupling include 10- µ F and 0.1- µ F capacitors
for each supply. A 1000-pF capacitor can be
used across the supplies as well for extremely
Computer simulation of circuit performance using
high-frequency return currents, but often is not
SPICE is often useful when analyzing the
required.
performance of analog circuits and systems. This is
particularly true for video and RF amplifier circuits
where parasitic capacitance and inductance can have
AND APPLICATIONS SUPPORT
a major effect on circuit performance. A SPICE model
for the THS4500 family of devices is available
Texas Instruments is committed to providing its
through the Texas Instruments web site (www.ti.com ).
customers with the highest quality of applications
The Product Information Center (PIC) is available for
support. To support this goal, an evaluation board
design assistance and detailed product information.
has been developed for the THS4500 family of fully
These models do a good job of predicting
differential amplifiers. The evaluation board can be
small-signal ac and transient performance under a
obtained by ordering through the Texas Instruments
wide variety of operating conditions. They are not
web site, www.ti.com , or through your local Texas
intended to model the distortion characteristics of the
Instruments sales representative. The schematic for
amplifier, nor do they attempt to distinguish between
the evaluation board is shown in Figure 93 with
the package types in their small-signal ac
default component values. Unpopulated footprints are
performance. Detailed information about what is and
shown to provide insight into design flexibility.
is not modeled is contained in the model file itself.
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