OPA191 Datasheet, PDF (35/45 Pages) Texas Instruments – Low Offset Voltage, Low Input Bias Current Op Amp

www.ti.com
11 Layout
OPA191, OPA2191, OPA4191
SBOS701 – DECEMEBER 2015
11.1 Layout Guidelines
For best operational performance of the device, use good PCB layout practices, including:
• 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.
– 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.
• Make sure to physically separate digital and analog grounds paying attention to the flow of the ground
current. 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. For more detailed
information refer to Circuit Board Layout Techniques, SLOA089.
• In order 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 65, 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.
• Clean the PCB following board assembly for best performance.
• Any precision integrated circuit may experience performance shifts due to moisture ingress into the plastic
package. After any aqueous PCB cleaning process, bake the PCB assembly 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.
Copyright © 2015, Texas Instruments Incorporated
Submit Documentation Feedback
35
Product Folder Links: OPA191 OPA2191 OPA4191