+

RIN

RG

RF

VOUT

VIN

TL971, TL972, TL974

www.ti.com

SLOS467H – OCTOBER 2006 – REVISED JANUARY 2015

10 Power Supply Recommendations

The TL97x devices are specified for operation from 2.7 to 12 V; many specifications apply from -40 °C to 125 °C.

CAUTION

Supply voltages larger than 15 V can permanently damage the device (see the

Absolute Maximum Ratings).

Place 0.1-

μF bypass capacitors close to the power-supply pins to reduce errors coupling in from noisy or high

impedance power supplies. For more detailed information on bypass capacitor placement, refer to the Layout

Guidelines.

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 and 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 21. Operational Amplifier Schematic for Noninverting Configuration

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