BC447 Datasheet, PDF (28/36 Pages) ON Semiconductor – High Voltage Transistors

THS4271
THS4275
SLOS397E − JULY 2002 − REVISED JANUARY 2004
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, Rf = 0 Ω
18
_ ^Rf
16
+
14
150 Ω
SOIC,
49.9 Ω
12
Rf = 100 Ω
10
8
SOIC, Rf = 200 Ω
6 Leadless MSOP, &
4
MSOP Rf = 0 Ω
2
0
−2
VIN = 100 mVPP
VS =±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.
28
www.ti.com
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
Rf = 50 Ω
13
+
150 Ω
11
49.9 Ω
Rf = 0 Ω
9
Rf = 100 Ω
7
5
Rf = 150 Ω
3
1
−1
−3 ^{VIN = 100 mVPP}
−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}
RL = 150 Ω
−3
VO = 100 mVPP
VS = ±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 G = +1 EVM
The peaking in the frequency response is due to the lead
inductance in the feedback path. Each pad and trace on a
PCB has an inductance associated with it, which in
conjunction with the inductance associated with the
package may cause peaking in the frequency response,
causing the device to become unstable.