TL971 Datasheet, PDF (13/33 Pages) Texas Instruments – OUTPUT RAIL-TO-RAIL VERY-LOW-NOISE OPERATIONAL AMPLIFIERS

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TL971, TL972, TL974
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
RIN
VIN
+
RG
RF
VOUT
Figure 21. Operational Amplifier Schematic for Noninverting Configuration
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