THS4271-EP Datasheet, PDF (21/44 Pages) Texas Instruments – LOW NOISE, HIGH SLEW RATE, UNITY GAIN STABLE VOLTAGE FEEDBACK AMPLIFIER

THS4271-EP
www.ti.com
HIGH-SPEED OPERATIONAL AMPLIFIERS
The THS4271 operational amplifier sets new
performance levels, combining low distortion, high
slew rates, low noise, and a unity-gain bandwidth in
excess of 1 GHz. To achieve the full performance of
the amplifier, careful attention must be paid to
printed-circuit board (PCB) layout and component
selection.
Applications Section Contents
• Wideband, Noninverting Operation
• Wideband, Inverting Gain Operation
• Single-Supply Operation
• Saving Power with Power-Down Functionality and
Setting Threshold Levels with the Reference Pin
• Power Supply Decoupling Techniques and
Recommendations
• Using the THS4271 as a DAC Output Buffer
• Driving an ADC With the THS4271
• Active Filtering With the THS4271
• Building a Low-Noise Receiver with the THS4271
• Linearity: Definitions, Terminology, Circuit
Techniques and Design Tradeoffs
• An Abbreviated Analysis of Noise in Amplifiers
• Driving Capacitive Loads
• Printed Circuit Board Layout Techniques for
Optimal Performance
• Power Dissipation and Thermal Considerations
• Performance vs Package Options
• Evaluation Fixtures, Spice Models, and
Applications Support
• Additional Reference Material
• Mechanical Package Drawings
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SGLS270C – DECEMBER 2004 – REVISED APRIL 2010
WIDEBAND, NONINVERTING OPERATION
The THS4271 is a unity gain stable, 1.4-GHz
voltage-feedback operational amplifier, with and
without power-down capability, designed to operate
from a single 5-V to 15-V power supply.
Figure 76 is the noninverting gain configuration of
2 V/V used to demonstrate the typical performance
curves. Most of the curves were characterized using
signal sources with 50-Ω source impedance, and with
measurement equipment presenting a 50-Ω load
impedance. In Figure 76, the 49.9-Ω shunt resistor at
the V_IN terminal matches the source impedance of the
test generator. The total 499-Ω load at the output,
combined with the 498-Ω total feedback network load,
presents the THS4271 with an effective output load of
249 Ω for the circuit of Figure 76.
Voltage feedback amplifiers, unlike current feedback
designs, can use a wide range of resistors values to
set their gain with minimal impact on their stability
and frequency response. Larger-valued resistors
decrease the loading effect of the feedback network
on the output of the amplifier, but this enhancement
comes at the expense of additional noise and
potentially lower bandwidth. Feedback resistor values
between 249 Ω and 1 kΩ are recommended for most
situations.
5 V _+VS
50 Ω Source
V_I
49.9 Ω
249 Ω
+
100 pF 0.1 µF 6.8 µF
+
THS4271
_
R_f
V_O
499 Ω
249 Ω
R_g
0.1 µF 6.8 µF
100 pF
+
−5 V ^−VS
Figure 76. Wideband, Noninverting
Gain Configuration
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