THS4271_16 Datasheet, PDF (31/50 Pages) Texas Instruments – LOW NOISE, HIGH SLEW RATE, UNITY GAIN STABLE VOLTAGE FEEDBACK AMPLIFIER

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DESIGN TOOLS
Performance vs Package Options
The THS4271 and THS4275 are offered in different
package options. However, performance may be
limited due to package parasitics and lead inductance
in some packages. In order to achieve maximum
performance of the THS4271 and THS4275, Texas
Instruments recommends using the leadless MSOP
(DRB) or MSOP (DGN) packages, in addition to
proper high-speed PCB layout. Figure 92 shows the
unity gain frequency response of the THS4271 using
the leadless MSOP, MSOP, and SOIC package for
comparison. Using the THS4271 and THS4275 in a
unity gain with the SOIC package may result in the
device becoming unstable. In higher gain
configurations, this effect is mitigated by the reduced
bandwidth. As such, the SOIC is suitable for
application with gains equal to or higher than +2 V/V
or (–1 V/V).
20
SOIC, R_f = 0 Ω
18
_ ^Rf
16
+
14
150 Ω
SOIC,
49.9 Ω
12
R_f = 100 Ω
10
8
SOIC, R_f = 200 Ω
6 Leadless MSOP, &
4
MSOP R_f = 0 Ω
2
0
−2
V_IN = 100 mV_PP
V_S =±5 V
−4
10 M
100 M
1G
f − Frequency − Hz
Figure 92. Effects of Unity Gain Frequency
Response for DIfferential Packages
Evaluation Fixtures, Spice Models, and
Applications Support
Texas Instruments is committed to providing its
customers with the highest quality of applications
support. To support this goal, evaluation boards have
been developed for the THS4271 operational
amplifier. Three evaluation boards are available: one
THS4271 and one THS4275, both are configurable
for different gains, and a third for a gain of +1
(THS4271 only). These boards are easy to use,
allowing for straightforward evaluation of the device.
These evaluation boards can be ordered through the
Texas Instruments web site, www.ti.com, or through
your local Texas Instruments sales representative.
Schematics for the evaluation boards are shown
below.
THS4271
THS4275
SLOS397F – JULY 2002 – REVISED OCTOBER 2009
The THS4271/THS4275 EVM board shown in
Figure 96 through Figure 99 is designed to
accommodate different gain configurations. Its default
component values are set to give a gain of 2. The
EVM can be configured in a gain of +1; however, it is
strongly not recommended. Evaluating the
THS4271/THS4275 in a gain of 1 using this EVM
may cause the part to become unstable. The stability
of the device can be controlled by adding a large
resistor in the feedback path, the performance is
sacrificed. Figure 93 shows the small-signal
frequency response of the THS4271 with different
feedback resistors in the feedback path. Figure 94 is
the small frequency response of the THS4271 using
the gain of 1 EVM.
17
15
_ ^Rf
R_f = 50 Ω
13
+
150 Ω
11
49.9 Ω
R_f = 0 Ω
9
R_f = 100 Ω
7
5
R_f = 150 Ω
3
1
−1
−3 ^VIN ^{= 100 mV}PP
−5 ^{VS = ±5 V}
10M
100M
1G
f − Frequency − Hz
Figure 93. Frequency Response vs Feedback
Resistor Using the EDGE #6439527 EVM
4
3
_
+
2
150 Ω
49.9 Ω
1
0
−1
−2 ^{Gain = 1}
R_L = 150 Ω
−3
V_O = 100 mV_PP
V_S = ±5 V
−4
100 k 1 M
10 M 100 M 1 G
f − Frequency − Hz
10 G
Figure 94. Frequency Response
Using the EDGE #6443547 EVM
Copyright © 2002–2009, Texas Instruments Incorporated
Product Folder Link(s): THS4271 THS4275
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