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THS4051 High Speed Operational Amplifier Evaluation Module
User's Guide
July 1999
Mixed-Signal Products
SLOU049
IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, AUTHORIZED, OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF TI PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI's publication of information regarding any third party's products or services does not constitute TI's approval, warranty or endorsement thereof.
Copyright (c) 1999, Texas Instruments Incorporated
Preface
Related Documentation From Texas Instruments
J
THS4051, THS4052 70-MHz HIGH-SPEED AMPLIFIERS (literature number SLOS238) This is the data sheet for the THS4051 operational amplifier integrated circuit that is used in the THS4051 evaluation module.
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
TI is a trademark of Texas Instruments Incorporated. PowerPAD is a trademark of Texas Instruments Incorporated.
Chapter Title--Attribute Reference
iii
iv
Running Title--Attribute Reference
Contents
1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 THS4051 EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Using the THS4051 EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 THS4051 EVM Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 General High-Speed Amplifier Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1-1 1-2 1-4 1-4 1-5 1-6
2
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.1 THS4051 High-Speed Operational Amplifier EVM Parts List . . . . . . . . . . . . . . . . . . . . . . 2-2 2.2 THS4051 EVM Board Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Chapter Title--Attribute Reference
v
Running Title--Attribute Reference
Figures
1-1 1-2 1-3 1-4 2-1 2-2 2-3 THS4051 Evaluation Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THS4051 EVM Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THS4051 EVM Frequency Response With Gain = +2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THS4051 EVM Frequency Response With Gain = -1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 1-3 1-5 1-5
THS4051 EVM Component Placement Silkscreen and Solder Pads . . . . . . . . . . . . . . . . . 2-2 THS4051 EVM PC Board Layout - Component Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 THS4051 EVM PC Board Layout - Back Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Tables
2-1 THS4051 EVM Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
vi
Chapter 1
General
This chapter details the Texas Instruments (TITM) THS4051 high-speed operational amplifier evaluation module (EVM), SLOP220. It includes a list of EVM features, a brief description of the module illustrated with a pictorial and a schematic diagram, EVM specifications, details on connecting and using the EVM, and a discussion on high-speed amplifier design considerations.
Topic
1.1 1.2 1.3 1.4 1.4 1.4
Page
Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 THS4051 EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Using The THS4051 EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 THS4051 EVM Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 General High-Speed Amplifier Design Considerations . . . . . . . . . . . 1-6
1.1 Feature Highlights
THS4051 high-speed operational amplifier EVM features include:
J J J J J J J
High Bandwidth -- 30 MHz, -3 dB @ 15 VCC & Gain = 2 5-V to 15-V Operation Inverting and Noninverting Single-Ended Inputs Module Gain Set to + 2 (Noninverting) and -1 (Inverting) -- Adjustable Through Component Change. Nominal 50- Impedance Inputs and Outputs Standard SMA Miniature RF Connectors Good Example of High-Speed Amplifier Design and Layout
General
1-1
Description
1.2 Description
The TI THS4051 high-speed operational amplifier evaluation module (EVM) is a complete high-speed amplifier circuit. It consists of the TI THS4051 high-speed, low-power operational amplifier IC, along with a small number of passive parts, mounted on a small circuit board measuring approximately 1.7 inch by 1.4 inch (Figure 1-1). The EVM uses standard SMA miniature RF connectors for inputs and outputs and is completely assembled, fully tested, and ready to use -- just connect it to power, a signal source, and a load (if desired).
Figure 1-1. THS4051 Evaluation Module
J1 -VCC J2 C1 GND +VCC C2
-IN GND INVERTING NONINVERTING R1 R3 R2 + + R4 TEXAS INSTRUMENTS J4 C3
+IN GND J3
SLOP220 THS4051 EVM Board
The THS4051 EVM is equipped with both noninverting and inverting inputs. The noninverting input is set for a gain of + 2 and the inverting input is set for a gain of -1. Each input is terminated with a 50- resistor to provide correct line impedance matching (Figure 1-2). The amplifier IC output is routed through a 50- resistor both to provide correct line impedance matching and to help isolate capacitive loading on the output of the amplifier. Capacitive loading directly on the output of the IC decreases the amplifier's phase margin and can result in peaking or oscillations.
GND
OUT
U1
C4
R5
1-2
General
Description
Figure 1-2. THS4051 EVM Schematic
-VCC GND VCC J1 1 2 3
+
C1 6.8 F
+
C2 6.8 F -IN Inverting R2 2 k J2 R1 49.9
2
VCC R4 2 k
7
C3 0.1 F
- U1 THS4051
6
R5 49.9
J4 Out
+IN Noninverting
J3 R3 49.9
3
+
4
C4 0.1 F
-VCC
The gain of the EVM inputs can easily be changed to support a particular application by simply changing the ratio of resistors R1, R4, and R5 as described in the following equations:
+ -R + -R4 R R2 R Noninverting Gain + 1 ) + 1 ) R2 R4 R1 R )
Inverting Gain
F G F G
In addition, some applications, such as those for video, may require the use of 75- cable and 75- EVM input termination and output isolation resistors. Any of the resistors on the EVM board can be replaced with a resistor of a different value; however, care must be taken because the surface-mount solder pads on the board are somewhat fragile and will not survive many desoldering/soldering operations. Note that external factors can significantly affect the effective gain of the EVM. For example, connecting test equipment with 50- input impedance to the EVM output will divide the output signal level by a factor of 2 (assuming the output isolation resistor on the EVM board remains 50 ). Similar effects can occur at the input, depending upon how the input signal sources are configured. The gain equations given above assume no signal loss in either the input or the output. The EVM circuit board is an excellent example of proper board layout for high-speed amplifier designs and can be used as a guide for user application board layouts.
General
1-3
THS4051 EVM Specifications
1.3 THS4051 EVM Specifications
Supply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 V to 15 V Supply current, ICC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 mA typ Input voltage, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC, max Output drive, IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 mA For complete THS4051 amplifier IC specifications and parameter measurement information, and additional application information, see the THS4051 data sheet, TI Literature Number SLOS216.
1.4 Using the THS4051 EVM
The THS4051 EVM operates from power-supply voltages ranging from 5 V to 15 V. As shipped, the inverting input gain of the module is set to -1, the noninverting input gain is set to 2, and signal inputs on the module are terminated for 50- nominal impedance cables. An oscilloscope is typically used to view and analyze the EVM output signal. 1) Ensure that all power supplies are set to OFF before making power supply connections to the THS4051 EVM. 2) Select the operating voltage for the EVM and connect appropriate split power supplies to the pads on the module marked -VCC and +VCC. 3) Connect the power supply ground to the module pad marked GND. 4) Connect an oscilloscope to the module SMA output connector (J4) through a 50- nominal impedance cable (an oscilloscope having a 50- input termination is preferred for examining very high frequency signals). 5) Set the power supply to ON. 6) Connect the signal input to either the noninverting input (J3) for a gain of 2, or to the inverting input (J2) for a gain of -1. Note that each input connector is terminated with a 50- resistor to ground. With a 50- source impedance, the voltage seen by the THS4051 amplifier IC on the module will be the source signal voltage applied to the EVM.
1/2
7) Verify the output signal on the oscilloscope. Note that the signal shown on an oscilloscope with a 50- input impedance will be the actual THS4051 amplifier IC output voltage. This is due to the voltage division between the output resistor (R5) and the oscilloscope input impedance.
1/2
1-4
General
THS4051 EVM Performance
1.5 THS4051 EVM Performance
Figure 1-3 shows the typical frequency response of the THS4051 EVM using the noninverting input (G = 2). Typical +0.1 dB bandwidths are 8 MHz and a - 3-dB bandwidth of 30 MHz with a 15 V power supply. These bandwidths remain consistent when the power supply drops to 5 V.
Figure 1-3. THS4051 EVM Frequency Response With Gain = +2
7 Amplitude 6 Output Amplitude - dB 5 4 3 2 1 0 VCC = 15 V & 5 V VO = 0.2 Vrms RL = 150 1M 10M f - Frequency - Hz Phase 30 0 -30 -60 -90 -120 -150 - 180 100M Output Phase - Degrees Output Phase - Degrees 60
-1 100K
Figure 1-4 shows the typical frequency response of the THS4051 EVM using the inverting input (G = -1). Typical - 0.1 dB bandwidths are 7 MHz and a - 3-dB bandwidth of 30 MHz with a 15 V power supply. These bandwidths remain consistent when the power supply drops to 5 V.
Figure 1-4. THS4051 EVM Frequency Response With Gain = -1
1 Amplitude 0 Output Amplitude - dB -1 Phase -2 -3 -4 -5 -6 VCC = 15 V & 5 V VO = 0.2 Vrms RL = 150 1M 10M f - Frequency - Hz 150 120 90 60 30 0 100M 210 180 240
-7 100K
General
1-5
General High-Speed Amplifier Design Considerations
1.6 General High-Speed Amplifier Design Considerations
The THS4051 EVM layout has been designed and optimized for use with high-speed signals and can be used as an example when designing THS4051 applications. Careful attention has been given to component selection, grounding, power supply bypassing, and signal path layout. Disregard of these basic design considerations could result in less than optimum performance of the THS4051 high-speed, low-power operational amplifier. Surface-mount components were selected because of the extremely low lead inductance associated with this technology. Also, because surface-mount components are physically small, the layout can be very compact. This helps minimize both stray inductance and capacitance. Tantalum power supply bypass capacitors (C1 and C2) at the power input pads help supply currents for rapid, large signal changes at the amplifier output. The 0.1 F power supply bypass capacitors (C3 and C4) were placed as close as possible to the IC power input pins in order to keep the PCB trace inductance to a minimum. This improves high-frequency bypassing and reduces harmonic distortion. A proper ground plane on both sides of the PCB should always be used with high-speed circuit design. This provides low-inductive ground connections for return current paths. In the area of the amplifier IC input pins, however, the ground plane was removed to minimize stray capacitance and reduce ground plane noise coupling into these pins. This is especially important for the inverting pin while the amplifier is operating in the noninverting mode. Because the voltage at this pin swings directly with the noninverting input voltage, any stray capacitance would allow currents to flow into the ground plane, causing possible gain error and/or oscillation. Capacitance variations at the amplifier IC input pin of less than 1 pF can significantly affect the response of the amplifier. In general, it is always best to keep signal lines as short and as straight as possible. Stripline techniques should also be incorporated when signal lines are greater than 1 inch in length. These traces should be designed with a characteristic impedance of either 50 or 75 , as required by the application. Such signal lines should also be properly terminated with an appropriate resistor. Finally, proper termination of all inputs and outputs should be incorporated into the layout. Unterminated lines, such as coaxial cable, can appear to be a reactive load to the amplifier IC. By terminating a transmission line with its characteristic impedance, the amplifier's load then appears to be purely resistive and reflections are absorbed at each end of the line. Another advantage of using an output termination resistor is that capacitive loads are isolated from the amplifier output. This isolation helps minimize the reduction in amplifier phase-margin and improves the amplifier stability for improved performance such as reduced peaking and settling times.
1-6
General
Chapter 2
Reference
This chapter includes a parts list and PCB layout illustrations for the THS4051 EVM.
Topic
2.1 2.2
Page
THS4051 High-Speed Operational Amplifier EVM Parts List . . . . . . . 2-2 THS4051 EVM Board Layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Reference
2-1
THS4051 High-Speed Operational Amplifier EVM Parts List
2.1 THS4051 High-Speed Operational Amplifier EVM Parts List
Table 2-1. THS4051 EVM Parts List
Reference C1, C2 C3, C4 J1 J2, J3, J4 R1, R3, R5 R2, R4 U1 PCB1 Description Capacitor, 6.8 F, 35 V, SM Capacitor, 0.1 F, ceramic, 10%, SM Terminal Block Connector, SMA 50- vertical PC mount, through-hole Resistor, 49.9 , 1%, 1/8 W, SM Resistor, 2 k, 1%, 1/8 W, SM IC, THS4051, operational amplifier PCB, THS4051 EVM 1206 1206 Size D 1206 Manufacturer/Digi-Key Part Number Sprague 293D685X9035D2T Sprague 11C1201E104M5NT Digi-Key ED1515-ND Amphenol ARF1205-ND Digi-Key P49.9CTR-ND Digi-Key P2.0KCTR-ND
SOIC-8 TI THS4051
2.2 THS4051 EVM Board Layouts
Board layout examples of the THS4051 EVM PCB are shown in the following illustrations. They are not to scale and appear here only as a reference.
Figure 2-1. THS4051 EVM Component Placement Silkscreen and Solder Pads
J1 -VCC J2 C1 GND +VCC C2
-IN GND INVERTING NONINVERTING R1 R3 R2 + + R4 TEXAS INSTRUMENTS J4 C3
U1
J3
SLOP220 THS4051 EVM Board
GND
GND
C4
OUT
+IN
R5
2-2
Reference
THS4051 EVM Board Layouts
Figure 2-2. THS4051 EVM PC Board Layout - Component Side
Figure 2-3. THS4051 EVM PC Board Layout - Back Side
Reference
2-3
2-4
Reference

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