OUT1

OUT2

IN1

í

IN1+

VCC

í

VCC+

IN2

í

IN2+

RG

RIN

RF

GND

VIN

VS-

GND

VS+

GND

Run the input traces as far

away from the supply lines

as possible

Only needed for

dual-supply

operation

Place components close to

device and to each other to

reduce parasitic errors

Use low-ESR, ceramic

bypass capacitor

(or GND for single supply)

Ground (GND) plane on another layer

+

RIN

RG

RF

VOUT

VIN

12

LP358, LP2904

SLOS475A – AUGUST 2005 – REVISED MAY 2017

www.ti.com

Product Folder Links: LP358 LP2904

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Copyright © 2005–2017, Texas Instruments Incorporated

11 Layout

11.1 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, as well as the

operational amplifier. 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

it is not possible to keep them separate, it is much better to cross the sensitive trace perpendicular as

opposed to in parallel with the noisy trace.

•

Place the external components as close to the device as possible. Keeping RF and RG close to the inverting

input minimizes parasitic capacitance, as shown in Layout Example.

•

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.

11.2 Layout Example

Figure 6. Operational Amplifier Schematic for Noninverting Configuration

Figure 7. Operational Amplifier Board Layout for Noninverting Configuration