THS3120_16 Datasheet, PDF (15/35 Pages) Texas Instruments – LOW-NOISE, HIGH-OUTPUT DRIVE, CURRENT-FEEDBACK OPERATIONAL AMPLIFIERS

THS3120
THS3121
www.ti.com........................................................................................................................................ SLOS420E – SEPTEMBER 2003 – REVISED OCTOBER 2009
APPLICATION INFORMATION
MAXIMUM SLEW RATE FOR REPETITIVE
SIGNALS
The THS3120 and THS3121 are recommended for
high slew rate pulsed applications where the internal
nodes of the amplifier have time to stabilize between
pulses. It is recommended to have at least 20-ns
delay between pulses.
The THS3120 and THS3121 are not recommended
for applications with repetitive signals (sine, square,
sawtooth, or other) that exceed 900 V/μs. Using the
part in these applications results in excessive current
draw from the power supply and possible device
damage.
For applications with high slew rate, repetitive signals,
the THS3091 and THS3095 (single), or THS3092 and
THS3096 (dual) are recommended.
WIDEBAND, NONINVERTING OPERATION
The THS3120 and THS3121 are unity-gain stable
130-MHz current-feedback operational amplifiers,
designed to operate from a ±5-V to ±15-V power
supply.
Figure 47 shows the THS3121 in a noninverting gain
of 2-V/V configuration typically used to generate the
Typical Characteristics. Most of the curves were
characterized using signal sources with 50-Ω source
impedance, and with measurement equipment
presenting a 50-Ω load impedance.
15 V _+VS
+
50 Ω Source
0.1 µF
6.8 µF
V_I
49.9 Ω
+
THS3120
_
R_F
49.9 Ω
50 Ω LOAD
649 Ω R_G
649 Ω
0.1 µF
6.8 µF
+
-V_S
-15 V
Figure 47. Wideband, Noninverting Gain
Configuration
Current-feedback amplifiers are highly dependent on
the feedback resistor R_F for maximum performance
and stability. Table 1 shows the optimal gain setting
resistors R_F and R_G 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
R_F. Conversely, increasing R_F decreases the
bandwidth, but stability is improved.
Table 1. Recommended Resistor Values for
Optimum Frequency Response
THS3120 AND THS3121 R_F AND R_G VALUES FOR MINIMAL
PEAKING WITH R_L = 50 Ω
GAIN (V/V)
SUPPLY VOLTAGE
(V)
R_G (Ω)
R_F (Ω)
±15
—
806
1
±5
—
909
±15
649
649
2
±5
750
750
±15
124
499
5
±5
124
499
±15
33.2
301
10
±5
33.2
301
±15
681
681
–1
±5
750
750
–2
±15 and ±5
340
681
–5
±15 and ±5
100
499
–10
±15 and ±5
36.5
365
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Product Folder Link(s): THS3120 THS3121
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