AD8003

Rev. A | Page 14 of 16

Minimizing the trace length and widening the trace from the

capacitors to the amplifier reduces the trace inductance. A

series inductance with the parallel capacitance can form a tank

circuit, which can introduce high frequency ringing at the

output. This additional inductance can also contribute to

increased distortion due to high frequency compression at the

output. The use of vias should be minimized in the direct path

to the amplifier power supply pins because vias can introduce

parasitic inductance, which can lead to instability. When

required, use multiple large diameter vias because this lowers

the equivalent parasitic inductance.

GROUNDING

The use of ground and power planes is encouraged as a method

of proving low impedance returns for power supply and signal

currents. Ground and power planes can also help to reduce

stray trace inductance and provide a low thermal path for the

amplifier. Ground and power planes should not be used under

any of the pins of the AD8003. The mounting pads and the

ground or power planes can form a parasitic capacitance at the

amplifiers input. Stray capacitance on the inverting input and

the feedback resistor form a pole, which degrades the phase

margin, leading to instability. Excessive stray capacitance on the

output also forms a pole, which degrades phase margin.