Texas Instruments THS4131 User Manual

THS4131

EVM User' s Guide for HighĆSpeed FullyĆDiffer ential Amplifier

User’s Guide

February 2001 Mixed-Signal Products

SLOU1 10

IMPORTANT NOTICE

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About This Manual

Preface

This manual is written to provide information about the evaluation module of the fully differential amplifier under test. Additionally, this document provides a good example of PCB design for high speed applications. The user should keep in mind the following points.

The design of the high-speed amplifier PCB is an elegant and sensitive process. Therefore, the user must approach the PCB design with care and awareness. It is recommend that the user initially review the datasheet of the device under test. It is also helpful to review the schematic and layout of the THS4131 EVM to determine the design techniques used in the evaluation board. In addition, it is recommended that the user review the application note

Fully-Differential Amplifiers

insight about differential amplifiers. This application note reviews the differential amplifiers and presents calculations for various filters

(literature number SLOA054B) to gain more

How to Use This Manual

Chapter 1—Introduction and Description Chapter 2—Using the THS4131 EVM Chapter 3—General High-Speed Amplifier Design Considerations

Read This First

iii

Related Documentation From Texas Instruments

Information About Cautions and Warnings

This book may contain cautions and warnings.

This is an example of a caution statement. A caution statement describes a situation that could potentially

damage your software or equipment.

This is an example of a warning statement. A warning statement describes a situation that could potentially

cause harm to you.

The information in a caution or a warning is provided for your protection. Please read each caution and warning carefully.

Related Documentation From Texas Instruments

THS4131 data sheet (literature number SLOS318)

THS4131 application report (literature number SLOA054A),

Fully-Differential Amplifiers

FCC Warning

This equipment is intended for use in a laboratory test environment only. It generates, uses, and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to subpart J of part 15 of FCC rules, which are designed to provide reasonable protection against radio frequency interference. Operation of this equipment in other environments may cause interference with radio communications, in which case the user at his own expense will be required to take whatever measures may be required to correct this interference.

Trademarks

PowerPAD is a trademark of Texas Instruments.

Running Title—Attribute Reference

Contents

1 Introduction and Description 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 Description 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 Evaluation Module Features 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.3 THS4131 EVM Specifications 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4 Schematic of the Populated Circuit (Default Configuration) 1-3. . . . . . . . . . . . . . . . . . . . . . .

1.5 THS4131 EVM Schematic 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.6 Additional Sample Schematics 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.7 THS4131 EVM Layout 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 Using the THS4131 EVM 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 Required Equipment 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Power Supply Setup 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3 Input and Output Setup 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.4 Testing the EVM Setup 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.5 Power Down Verification 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.6 Measuring the Frequency Response 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.7 Butterworth Filter 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.8 THS4131 EVM Bill of Materials 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 General High-Speed Amplifier Design Considerations 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter Title—Attribute Reference

Running Title—Attribute Reference

Figures

1–1 Schematic of the Populated Circuit on the EVM (Default Configuration) 1-3. . . . . . . . . . . . . .

1–2 Schematic 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–3 Fully-Differential In/Fully-Differential Out, Without Transformer 1-5. . . . . . . . . . . . . . . . . . . . . .

1–4 Fully-Differential In/Fully-Differential Out, Utilizing Transformer 1-5. . . . . . . . . . . . . . . . . . . . . .

1–5 VICR Level Shifter 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–6 Butterworth Filter With Multiple Feedback 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–7 Top Layer (Silkscreen) 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–8 Top (Layer 1) (Signals) 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–9 Internal Plane (Layer 2) (Ground Plane) 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–10 Internal Plane (Layer 3) (+ VCC Plane) 1-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1–11 Bottom (Layer 4) (Ground and Signal) 1-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–1 Power Supply Connection 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–2 Signal Connections 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–3 Driver 1 Output Signal 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–4 Multiple Feedback Filter Circuit 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2–5 Gain vs Phase 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tables

2–1 THS4131 EVM Bill of Materials 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1

Introduction and Description

The Texas Instruments THS4131 evaluation module (EVM) helps designers evaluate the performance of the THS4131 operational amplifier. Also, this EVM is a good example of high-speed PCB design.

This document details the Texas Instruments THS4131 high-speed operational amplifier evaluation module (EVM). It includes a list of EVM features, a brief description of the module illustrated with a series of schematic diagrams, EVM specifications, details on connecting and using the EVM, and a discussion of high-speed amplifier design considerations.

This EVM enables the user to implement various circuits to clarify the available configurations presented by the schematic of the EVM. In addition, the schematic of the default circuit has been added to depict the components mounted on the EVM when it is received by the customer. This configuration correlates to the single input/differential output signal.

Other sample circuits are presented to show how the user can implement other circuit configurations such as differential input/differential output signal, transformer utilization on the input and output terminals, VICR level shifter, and Butterworth filter with multiple feedback. The user may be able to create and implement circuit configurations in addition to those presented in this document using the THS4131 EVM.

Topic Page

1.1 Description 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 Evaluation Module Features 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.3 THS4131 EVM Specification 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4 Schematic of the Populated Circuit (Default Configuration) 1-3. . . . . . .

1.5 THS4131 EVM Schematic 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.6 Additional Sample Schematics 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.7 THS4131 EVM Layout 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction and Description

1-1

Description

1.1 Description

The THS4131 EVM is a good example of PCB design and layout for high-speed operational amplifier applications. It is a complete circuit for the high-speed operational amplifier. The EVM is made of the THS4131 high-speed operational amplifier, a number of passive components, and various features and footprints that enable the user to experiment, test, and verify various operational amplifier circuit implementations. The board measures 4.5 inches in length by 2.5 inches in width. populated for a single-ended input amplifier (see Figure 1-2 for populated circuits). The outputs (V ended. Gain is set to one and can be changed by changing the ratios of the feedback and gain resistors (see the device datasheet for recommended resistor values). The user may populate various footprints on the evaluation module board to verify filter designs or perform other experiments. Each input is terminated with a 50-Ω resistor to provide correct line-impedance matching.

1.2 Evaluation Module Features

THS4131 high-speed operational amplifier EVM features include:

Initially, this board is

and VO–) can be tested differentially or single

O+

Voltage supply operation range: 5-V to ±15-V operation (see the device data sheet)

Single and differential input and output capability

Nominal 50-Ω input and output termination resistors. They can be configured according to the application requirement.

direct input control (see schematic and the device data sheet)

OCM

pin can be controlled via transformer center-tap (see

OCM

schematic)

Shutdown pin control, JU1 (if applicable to the device, see the device data sheet)

Input and output transformer footprints for changing single-ended signals to differential signals

Footprint for high-precision, balanced feedback and gain resistors (0.01% or better)

Footprints for low-pass filter implementation (see application note SLOA054A)

Footprints for antialiasing filter implementation (see application note SLOA054A)

Differential probe terminals on input and output nodes for differential probe insertion

1-2

Various GND and signal test points on the PCB

Circuit schematic printed on the back of the EVM

A good example of high-speed amplifier PCB design and layout

Introduction and Description

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