Chapter 4

The THS4503EVM layout has been designed for use with high-speed signals and can be used as an example when designing PCBs incorporating the THS4503. Careful attention has been given to component selection, grounding, power supply bypassing, and signal path layout. Disregarding these basic design considerations could result in less than optimum performance of the THS4503 high-speed operational amplifier. Surface- mount components were selected because of the extremely low lead inductance associated with this technology. This helps minimize both stray inductance and capacitance. Also, because surface-mount components are physically small, the layout can be very compact.

Tantalum power supply bypass capacitors at the power input pads help filter switching transients from the laboratory power supply. Power supply bypass capacitors are placed as close as possible to the IC power input pins in order to minimize the return path impedance. This improves high frequency bypassing and reduces harmonic distortion. The GND side of these capacitors should be located close to each other, minimizing the differential current loops associated with differential output currents. If poor high frequency performance is observed, replace the 0.1-µF capacitors with microwave capacitors with a self-resonance at the frequency that produces trouble. A proper ground plane on both sides of the PCB should be used with high-speed circuit design. This provides low-inductive ground connections for return current paths.

In the area of the amplifier input pins, however, the ground plane has been removed to minimize stray capacitance and reduce ground plane noise coupling into these pins. This is especially important for the inverting input pin. As low as 1 pF capacitance at the inverting input can significantly affect the response of the amplifier or even oscillation.

In general, it is best to keep signal lines as short and as straight as possible. Incorporation of microstrip or stripline techniques is also recommended when signal lines are greater than 1 inch in length. These traces must be designed with a characteristic impedance of either 50 Ω or 75 Ω, as required by the application. Such a signal line must also be properly terminated with an appropriate resistor.

High-Speed Amplifier PCB Layout Tips

4-1

Page 22 Page 24
Page 23
Image 23
Texas Instruments THS4503EVM manual High-Speed Amplifier PCB Layout Tips
Page 22 Page 24

THS4503EVM specifications

The Texas Instruments THS4503EVM is a high-performance evaluation module designed to showcase the capabilities of the THS4503, a high-speed voltage feedback amplifier. This EVM is ideal for engineers and designers looking to evaluate the performance characteristics of this amplifier in real-world applications, including video signal processing, data acquisition systems, and RF applications.

One of the main features of the THS4503EVM is its exceptional bandwidth performance. The THS4503 amplifier boasts a wide bandwidth that extends up to 1 GHz, making it suitable for applications where high frequency signals need to be processed with minimal distortion. The high slew rate of 3000 V/µs allows for rapid signal changes, ensuring that fast transients are accurately captured without significant overshoot or ringing.

The design of the THS4503EVM also incorporates a low noise characteristic, making it an excellent choice for sensitive applications where signal integrity is paramount. The EVM's Input Voltage Noise Density is remarkably low, contributing to cleaner signal amplification and making it a valuable tool for testing low-level signals.

Another significant characteristic of the THS4503EVM is its flexibility in configuration. The evaluation module is equipped with connectors that allow users to quickly set up various input and output configurations. This provides engineers with the ability to easily test a wide range of operating conditions, including voltage gain settings, power supply configurations, and load conditions, all ideal for diverse application scenarios.

Furthermore, the THS4503EVM supports both single and dual power supply options, accommodating various system designs. It can operate on a supply voltage range from ±2.5 V to ±5 V, allowing users to tailor the functionality of the amplifier to their specific power requirements.

In terms of technology, the THS4503 integrates precision feedback circuitry and advanced manufacturing techniques, ensuring minimal drift and excellent linearity. The module is designed for simplicity and user-friendliness, with comprehensive documentation and application information available from Texas Instruments, aiding users in achieving optimal performance.

In summary, the Texas Instruments THS4503EVM is a powerful evaluation tool for the THS4503 amplifier, featuring high bandwidth, low noise, flexible configuration options, and robust support for various supply voltages. Its capabilities make it an invaluable resource for engineers working across a wide range of high-speed signal applications.
Top Page Image Contents