8.3 Power Supply Recommendations

The OPAx863A is intended to operate on supplies ranging from 2.7 V to 12.6 V. The OPAx863A devices operate

on single-sided supplies, split and balanced bipolar supplies, or unbalanced bipolar supplies. Operating from a

single supply has numerous advantages. The dc errors, due to the –PSRR term, can be minimized with the

negative supply at ground. Typically, ac performance improves slightly at 10

‑V operation with minimal increase

in supply current. Minimize the distance (< 0.1 in) from the power supply pins to high-frequency, 0.01

‑µF

decoupling capacitors. A larger capacitor (2.2 µF typical) is used along with a high-frequency, 0.01

‑µF supply-

decoupling capacitor at the device supply pins. Only the positive supply has these capacitors for single-supply

operation. Use these capacitors from each supply to ground when a split-supply is used. If necessary, place the

larger capacitors further from the device and share these capacitors among several devices in the same area

of the printed circuit board (PCB). An optional supply decoupling capacitor across the two power supplies (for

split-supply operation) reduces second harmonic distortion.

8.4 Layout

8.4.1 Layout Guidelines

Achieving optimum performance with a high-frequency amplifier (like the OPAx863A) requires careful attention

to board layout parasitics and external component types. The High Speed Amplifiers Generic DSN Evaluation

Module user's guide can be used as a reference when designing the circuit board. Recommendations that

optimize performance includes the following:

1. Minimize parasitic capacitance to any ac ground for all of the signal I/O pins. Parasitic capacitance on

the output and inverting input pins can cause instability on the noninverting input and can react with the

source impedance to cause unintentional band-limiting. Open a window around the signal I/O pins in all of

the ground and power planes around those pins to reduce unwanted capacitance. Otherwise, ground and

power planes must be unbroken elsewhere on the board.

2. Minimize the distance (< 0.1 in) from the power-supply pins to high-frequency 0.01

‑µF decoupling

capacitors. Avoid narrow power and ground traces to minimize inductance between the pins and the

decoupling capacitors. Always decouple the power-supply connections these capacitors. Use larger (2.2

‑µF

to 6.8

‑µF) decoupling capacitors, effective at lower frequency, on the supply pins. These capacitors can be

placed somewhat farther from the device and shared among several devices in the same area of the PCB.

3. Carefully select and place external components to preserve the high-frequency performance of the

OPAx863A. Use low-reactance-type resistors. Surface-mount resistors work best and allow a tighter overall

layout. Place other network components, such as noninverting input termination resistors, close to the

package. Keep resistor values as low as possible and consistent with load-driving considerations. Lower the

resistor values to keep the resistor noise terms low and minimize the effect of the parasitic capacitance.

Lower resistor values, however, increase the dynamic power consumption because RF and RG become part

of the amplifier output load network.

OPA863A, OPA2863A

SBOSA95D – MAY 2022 – REVISED DECEMBER 2023

www.ti.com

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