
APPLICATION INFORMATION
Wideband Noninverting Operation
Wideband Inverting Gain Operation
_
+
THS3201
RF
768
49.9
100 pF
0.1
F
6.8
F
-VS
-7.5 V
RG
50
Source
+
VI
100 pF
0.1
F
6.8
F
+
+VS
7.5 V
50
768
49.9
_
+
THS3201
RG
287
100 pF
0.1
F
6.8
F
-VS
-7.5 V
50
Source
+
VI
100 pF
0.1
F
6.8
F
+
+VS
7.5 V
RF
576
RM
60.4
50
49.9
SGLS283B – APRIL 2005 – REVISED JANUARY 2009 ..................................................................................................................................................... www.ti.com
Table 1. Recommended Resistor Values for
Optimum Frequency Response
The THS3201 is a unity gain stable 1.8-GHz
THS3201 RF for AC When Rload = 100
current-feedback operational amplifier, designed to
Gain
Supply Voltage
RG
RF
operate from a ±3.3-V to ±7.5-V power supply.
(V/V)
(V)
(
)
(
)
Figure 56 shows the THS3201 in a noninverting gain
±7.5
—
1.2 k
1
of 2-V/V configuration typically used to generate the
±5
—
1.2 k
performance
curves.
Most
of
the
curves
are
±7.5
768
characterized using signal sources with 50-
source
2
±5
715
impedance,
and
with
measurement
equipment
presenting a 50-
load impedance. The 49.9- shunt
±7.5
154.9
619
5
resistor at the VI terminal in Figure 56 matches the ±5
143
576
source impedance of the test generator.
±7.5
54.9
487
10
±5
51.1
464
±7.5
619
–1
±5
576
–2
±7.5 and ±5
287
576
–5
±7.5 and ±5
110
549
–10
±7.5 and ±5
49.9
499
Figure 57 shows the THS3201 is a typical inverting
gain configuration, where the input and output
impedances and signal gain from
Figure 56 are
retained in an inverting circuit configuration.
Figure 56. Wideband Noninverting Gain
Configuration
Unlike voltage-feedback amplifiers, current-feedback
amplifiers are highly dependent on the feedback
resistor RF for maximum performance and stability.
Table 1 shows the optimal gain setting resistors RF and RG at different gains to give maximum bandwidth
with minimal peaking in the frequency response.
Higher bandwidths can be achieved, at the expense
of added peaking in the frequency response, by using
even lower values for RF. Conversely, increasing RF
decreases the bandwidth, but stability is improved.
Figure 57. Wideband Inverting Gain Configuration
18
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