THS4221 Datasheet, PDF (14/41 Pages) Texas Instruments – LOW-DISTORTION, HIGH-SPEED, RAIL-TO-RAIL OUTPUT OPERATIONAL AMPLIFIERS

THS4221, THS4225
THS4222, THS4226
SLOS399G − AUGUST 2002 − REVISED JANUARY 2004
www.ti.com
APPLICATION INFORMATION
HIGH-SPEED OPERATIONAL AMPLIFIERS
The THS4222 family of operational amplifiers is a family of
single and dual, rail-to-rail output voltage feedback
amplifiers. The THS4222 family combines both a high
slew rate and a rail-to-rail output stage.
The THS4225 and THS4226 provides a power-down
mode, providing the ability to save power when the
amplifier is inactive. A reference pin is provided to allow the
user the flexibility to control the threshold levels of the
power-down control pin.
Applications Section Contents
D Wideband, Noninverting Operation
D Wideband, Inverting Gain Operation
D Single Supply Operation
D Saving Power With Power-Down Functionality and
Setting Threshold Levels With the Reference Pin
D Power Supply Decoupling Techniques and
Recommendations
D Driving an ADC With the THS4222
D Active Filtering With the THS4222
D An Abbreviated Analysis of Noise in Amplifiers
D Driving Capacitive Loads
D Printed Circuit Board Layout Techniques for Optimal
Performance
D Power Dissipation and Thermal Considerations
D Evaluation Fixtures, Spice Models, and Applications
Support
D Additional Reference Material
D Mechanical Package Drawings
5V
+V_S
+
50 Ω Source
100 pF 0.1 µF 6.8 µF
V_I
49.9 Ω
+
THS4222
_
R_f
V_O
499 Ω
1.3 kΩ R_g
1.3 kΩ
0.1 µF 6.8 µF
100 pF
+
−5 V ^−VS
Figure 29. Wideband, Noninverting Gain
Configuration
WIDEBAND, INVERTING OPERATION
Since the THS4222 family are general-purpose, wideband
voltage-feedback amplifiers, several familiar operational
amplifier applications circuits are available to the designer.
Figure 30 shows a typical inverting configuration where
the input and output impedances and noise gain from
Figure 29 are retained in an inverting circuit configuration.
Inverting operation is one of the more common
requirements and offers several performance benefits.
The inverting configuration shows improved slew rates
and distortion due to the pseudo-static voltage maintained
on the inverting input.
WIDEBAND, NONINVERTING OPERATION
The THS4222 is a family of unity gain stable rail-to-rail
output voltage feedback operational amplifiers, with and
without power-down capability, designed to operate from
a single 3-V to 15-V power supply.
Figure 29 is the noninverting gain configuration of 2 V/V
used to demonstrate the typical performance curves.
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 1 kΩ and 2 kΩ are
recommended for most situations.
5V
+V_S
+
100 pF 0.1 µF 6.8 µF
C_T
0.1 µF
R_T
649 Ω
50 Ω Source
R_g
V_I
1.3 kΩ
R_M
52.3 Ω
+
THS4222
_
V_O
499 Ω
R_f
1.3 kΩ
100 pF
0.1 µF
6.8 µF
+
−5 V ^−VS
Figure 30. Wideband, Inverting Gain
Configuration
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