OPA690 datasheet(14/40 Pages) TI

14 / 40 page

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

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.

THS4222

1.3 kΩ

49.9 Ω

100 pF

0.1 µF 6.8 µF

−VS

−5 V

50 Ω Source

100 pF 0.1 µF 6.8 µF

+VS

5 V

499 Ω

1.3 kΩ

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.

THS4222

1.3 kΩ

649 Ω

100 pF

0.1 µF

6.8 µF

−VS

−5 V

50 Ω Source

100 pF

0.1 µF

6.8 µF

+VS

5 V

0.1 µF

1.3 kΩ

52.3 Ω

499 Ω

Figure 30. Wideband, Inverting Gain

Configuration

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