Datasheet

_
+
THS4271
R
f
249 Ω
49.9 Ω
100 pF
0.1 µF 6.8 µF
−V
S
−5 V
R
g
50 Ω Source
+
V
I
100 pF
0.1 µF 6.8 µF
+
+V
S
5 V
V
O
499 Ω
249 Ω
THS4271
THS4275
SLOS397F –JULY 2002–REVISED OCTOBER 2009 www.ti.com
HIGH-SPEED OPERATIONAL AMPLIFIERS WIDEBAND, NONINVERTING OPERATION
The THS4271 and the THS4275 operational The THS4271 and the THS4275 are unity gain
amplifiers set new performance levels, combining low stable, 1.4-GHz voltage-feedback operational
distortion, high slew rates, low noise, and a unity-gain amplifiers, with and without power-down capability,
bandwidth in excess of 1 GHz. To achieve the full designed to operate from a single 5-V to 15-V power
performance of the amplifier, careful attention must supply.
be paid to printed-circuit board (PCB) layout and
Figure 75 is the noninverting gain configuration of 2
component selection.
V/V used to demonstrate the typical performance
The THS4275 provides a power-down mode, curves. Most of the curves were characterized using
providing the ability to save power when the amplifier signal sources with 50-Ω source impedance, and with
is inactive. A reference pin is provided to allow the measurement equipment presenting a 50-Ω load
user the flexibility to control the threshold levels of the impedance. In Figure 75, the 49.9-Ω shunt resistor at
power-down control pin. the V
IN
terminal matches the source impedance of the
test generator. The total 499-Ω load at the output,
Applications Section Contents combined with the 498-Ω total feedback network load,
presents the THS4271 and THS4275 with an
• Wideband, Noninverting Operation
effective output load of 249 Ω for the circuit of
• Wideband, Inverting Gain Operation
Figure 75.
• Single-Supply Operation
Voltage feedback amplifiers, unlike current feedback
• Saving Power with Power-Down Functionality and
designs, can use a wide range of resistors values to
Setting Threshold Levels with the Reference Pin
set their gain with minimal impact on their stability
• Power Supply Decoupling Techniques and
and frequency response. Larger-valued resistors
Recommendations
decrease the loading effect of the feedback network
• Using the THS4271 as a DAC Output Buffer
on the output of the amplifier, but this enhancement
• Driving an ADC With the THS4271
comes at the expense of additional noise and
potentially lower bandwidth. Feedback resistor values
• Active Filtering With the THS4271
between 249 Ω and 1 kΩ are recommended for most
• Building a Low-Noise Receiver with the THS4271
situations.
• 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
space
space
space
Figure 75. Wideband, Noninverting
space
Gain Configuration
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Product Folder Link(s): THS4271 THS4275