OPA1641 Datasheet, PDF (27/31 Pages) Texas Instruments – High-Performance, JFET-Input AUDIO OPERATIONAL AMPLIFIERS

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10 Layout
OPA1641, OPA1642, OPA1644
SBOS484C – DECEMBER 2009 – REVISED DECEMBER 2015
10.1 Layout Guidelines
For best operational performance of the device, use good PCB layout practices, including:
• Noise can propagate into analog circuitry through the power pins of the circuit as a whole and op amp
itself. Bypass capacitors are used to reduce the coupled noise by providing low-impedance power
sources local to the analog circuitry.
– Connect low-ESR, 0.1-µF ceramic bypass capacitors between each supply pin and ground, placed as
close to the device as possible. A single bypass capacitor from V+ to ground is applicable for single-
supply applications.
• Separate grounding for analog and digital portions of circuitry is one of the simplest and most-effective
methods of noise suppression. One or more layers on multilayer PCBs are usually devoted to ground
planes. A ground plane helps distribute heat and reduces EMI noise pickup. Make sure to physically
separate digital and analog grounds paying attention to the flow of the ground current. For more detailed
information refer to Circuit Board Layout Techniques, SLOA089.
• To reduce parasitic coupling, run the input traces as far away from the supply or output traces as
possible. If these traces cannot be kept separate, crossing the sensitive trace perpendicular is much
better as opposed to in parallel with the noisy trace.
• Place the external components as close to the device as possible. As shown in Figure 42, keeping RF
and RG close to the inverting input minimizes parasitic capacitance.
• Keep the length of input traces as short as possible. Always remember that the input traces are the most
sensitive part of the circuit.
• Consider a driven, low-impedance guard ring around the critical traces. A guard ring can significantly
reduce leakage currents from nearby traces that are at different potentials.
• Cleaning the PCB following board assembly is recommended for best performance.
• Any precision integrated circuit may experience performance shifts due to moisture ingress into the
plastic package. Following any aqueous PCB cleaning process, baking the PCB assembly is
recommended to remove moisture introduced into the device packaging during the cleaning process. A
low temperature, post cleaning bake at 85°C for 30 minutes is sufficient for most circumstances.
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Product Folder Links: OPA1641 OPA1642 OPA1644