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| THS3122 Datasheet, PDF (16/43 Pages) Texas Instruments – LOW-NOISE, HIGH-SPEED, 450 mA CURRENT FEEDBACK AMPLIFIERS | |||
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THS3122, THS3125
SLOS382E â SEPTEMBER 2001 â REVISED MAY 2015
www.ti.com
8.3 Device Functional Modes
8.3.1 Wideband, Noninverting Operation
The THS3125 and THS3122 are unity gain stable 130-MHz current-feedback operational amplifiers, designed to
operate from a ±5-V to ±15-V power supply.
Figure 37 shows the THS3125 in a noninverting gain of 2-V/V configuration used to generate the typical
characteristic curves. Most of the curves were characterized using signal sources with 50-Ω source impedance
and with measurement equipment that presents a 50-Ω load impedance.
+15 V
+VS
50-W Source
VI
49.9 W
THS3125
470 W
RF
470 W
RG
-VS
-15 V
0.1 mF
49.9 W
6.8 mF
50-W Load
0.1 mF
6.8 mF
Figure 37. Wideband, Noninverting Gain Configuration
Current-feedback amplifiers are highly dependent on the feedback resistor RF for maximum performance and
stability. Table 2 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.
Table 2. Recommended Resistor Values For Optimum Frequency Response
THS3125 and THS3122 RF and RG VALUES FOR MINIMAL PEAKING WITH RL = 50 Ω, ±5-V to ±15-V POWER SUPPLY
GAIN (V/V)
RG (Ω)
RF (Ω)
1
â
560
2
470
470
4
66.5
200
8.3.2 Wideband, Inverting Operation
Figure 38 shows the THS3125 in a typical inverting gain configuration where the input and output impedances
from Figure 37 are retained in an inverting circuit configuration.
+15 V
+VS
50-W Source
VI
RG
470 W
56.2 W
RM
THS3125
470 W
RF
0.1 mF
49.9 W
6.8 mF
50-W Load
-VS
-15 V
0.1 mF
6.8 mF
Figure 38. Wideband, Inverting Gain Configuration
16
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Product Folder Links: THS3122 THS3125
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