AD8067(Rev0) Ver la hoja de datos (PDF) - Analog Devices
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AD8067 Datasheet PDF : 24 Pages
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GROUNDING
To minimize parasitic inductances and ground loops in high speed,
densely populated boards, a ground plane layer is critical.
Understanding where the current flows in a circuit is critical in the
implementation of high speed circuit design. The length of the
current path is directly proportional to the magnitude of the
parasitic inductances and thus the high frequency impedance of the
path. Fast current changes in an inductive ground return will create
unwanted noise and ringing.
The length of the high frequency bypass capacitor leads is critical.
A parasitic inductance in the bypass grounding will work against
the low impedance created by the bypass capacitor. Because load
currents flow from supplies as well as ground, the load should be
placed at the same physical location as the bypass capacitor ground.
For large values of capacitors, which are intended to be effective at
lower frequencies, the current return path length is less critical.
AD8067
POWER SUPPLY BYPASSING
Power supply pins are actually inputs and care must be taken to
provide a clean, low noise dc voltage source to these inputs. The
bypass capacitors have two functions:
1. Provide a low impedance path for unwanted frequencies
from the supply inputs to ground, thereby reducing the
effect of noise on the supply lines
2. Provide localized charge storage—this is usually
accomplished with larger electrolytic capacitors
Decoupling methods are designed to minimize the bypassing
impedance at all frequencies. This can be accomplished with a
combination of capacitors in parallel to ground. Good quality
ceramic chip capacitors (X7R or NPO) should be used and always
kept as close to the amplifier package as possible. A parallel
combination of a 0.1 µF ceramic and a 10 µF electrolytic, covers a
wide range of rejection for unwanted noise. The 10 µF capacitor is
less critical for high frequency bypassing, and in most cases, one
per supply line is sufficient.
Rev. 0 | Page 19 of 24
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