AD8132WARMZ-R71 datasheet(26/33 Pages) AD

26 / 33 page

AD8132

Rev. I | Page 25 of 32

LAYOUT, GROUNDING, AND BYPASSING

As a high speed part, the AD8132 is sensitive to the printed

circuit board (PCB) environment in which it operates. Realizing

its superior specifications requires attention to various details of

good high speed PCB design.

The first requirement is a good solid ground plane that covers as

much of the board area around the AD8132 as possible. The only

exception to this is that the two input pins (Pin 1 and Pin 8) are

kept a few millimeters from the ground plane and that ground

be removed from inner layers and the opposite side of the board

under the input pins. This minimizes the stray capacitance on

these nodes and helps preserve the gain flatness vs. the frequency.

Bypass the power supply pins as close as possible to the device

to the nearby ground plane and use good high frequency ceramic

chip capacitors. Do this bypassing with a capacitance value

of 0.01 μF to 0.1 μF for each supply. Farther away, provide low

frequency bypassing with 10 μF tantalum capacitors from each

supply to ground.

Keep the signal routing short and direct to avoid parasitic effects.

Wherever there are complementary signals, a symmetrical

layout with matched lengths must be provided to the extent

possible to maximize the balance performance. When running

differential signals over a long distance, place the traces on

the PCB close together or twist together any differential wiring

to minimize the area of the loop that is formed. This reduces

the radiated energy and makes the circuit less susceptible to

interference.

CIRCUITS

RF1

RF2

RG1

RG2

Figure 67. Typical Four-Resistor Feedback Circuit

RF2

RG2

VIN

Figure 68. Typical Circuit with β1 = 0

RF1

RG1

Figure 69. Typical Circuit with β2 = 1

VIN

Figure 70. G = +2 Circuit with β1 = 0, Without Resistors

RF1

RG1

VIN

Figure 71. Typical Circuit with β2 = 0

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