-4
-3
-2
-1
0
1
2
3
4
5
100 k
1 M
10 M
100 M
1 G
10 G
f - Frequency - Hz
Small
Signal
Gain
-
dB
_
+
49.9
499
PIN = -7 dBm
VS = ±5 V
L(nH) + K ln
2
W ) T
) 0.223
W ) T ) 0.5
where
W = Width of trace in inches.
= Length of the trace in inches
.
T = Thickness of the trace in inches.
K = 5.08 for dimensions in inches, and K = 2 for dimensions
in cm.
-5
-3
-1
1
3
5
7
9
11
13
15
17
10 M
100 M
1 G
f - Frequency - Hz
Small
Signal
Gain
-
dB
10 G
_
+
Rf
49.9
499
PIN = -7 dBm
VS = ±5 V
Rf = 200
Rf = 100
Rf = 0
Rf = 50
SLOS400E – SEPTEMBER 2002 – REVISED SEPTEMBER 2009 ................................................................................................................................... www.ti.com
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
THS4211
operational
amplifier. Three evaluation boards are available: one
THS4211 and one THS4215, both configurable for
different gains, and a third for untiy gain (THS4211
only). These boards are easy to use, allowing for
straightforward
evaluation
of
the
device.
These
evaluation boards can be ordered through the Texas
local
Texas
Instruments
sales
representative.
Schematics for the evaluation boards are shown
Figure 94. Frequency Response Using the
below.
EDGE #6443547 G = +1 EVM
The
THS4211/THS4215
EVM
board
shown
in
The frequency-response peaking is due to the lead
gain configurations. Its default component values are
inductance in the feedback path. Each pad and trace
set to give a gain of 2. The EVM can be configured
on a PCB has an inductance associated with it, which
for
unity-gain;
however,
it
is
strongly
not
in conjunction with the inductance associated with the
recommended. Evaluating the THS4211/THS4215 in
package may cause frequency-response peaking,
unity-gain using this EVM may cause the device to
causing the device to become unstable.
become unstable. The stability of the device can be
controlled by adding a large resistor in the feedback
In order to achieve the maximum performance of the
path, but performance is sacrificed.
Figure 93 shows
device, PCB layout is very critical. Texas Instruments
the small-signal frequency response of the THS4211
has developed an EVM for the evaluation of the
with different feedback resistors in the feedback path.
THS4211 configured for a gain of 1. The EVM is
Figure 94 is the small frequency response of the
THS4211 using the unity-gain EVM.
designed to minimize peaking in the unity-gain
configuration.
Minimizing the inductance in the feedback path is
critical for reducing the peaking of the frequency
response in unity-gain. The recommended maximum
inductance allowed in the feedback path is 4 nH. This
(8)
space
Figure 93. Frequency Response vs Feedback
Resistor Using the EDGE #6439527 EVM
30
Copyright 2002–2009, Texas Instruments Incorporated