Texas Instruments THS3115EVM Evaluation Module THS3115EVM THS3115EVM 데이터 시트
제품 코드
THS3115EVM
4-1
General High-Speed Amplifier Design Considerations
General High-Speed Amplifier Design
Considerations
The THS3115/25 EVM layout has been designed for use with high-speed
signals and can be used as an example when designing PCBs incorporating
the THS3115/25. 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 THS3115/25 high-speed operational amplifier. Surface-
mount components are 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.
signals and can be used as an example when designing PCBs incorporating
the THS3115/25. 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 THS3115/25 high-speed operational amplifier. Surface-
mount components are 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. The 0.1-mF 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. If poor high frequency
performance is observed, replace the 0.1-mF 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.
switching transients from the laboratory power supply. The 0.1-mF 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. If poor high frequency
performance is observed, replace the 0.1-mF 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 is 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 in the single-ended to differential 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. This could cause possible gain error and/or oscillation. Capacitance
variations at the amplifier input pin of greater than 1 pF can significantly affect
the response of the amplifier.
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 in the single-ended to differential 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. This could cause possible gain error and/or oscillation. Capacitance
variations at the amplifier input pin of greater than 1 pF can significantly affect
the response of the amplifier.
Chapter 4