Generally, a good high frequency
layout keeps power supply and ground traces away from the inverting input and output
pins. Parasitic capacitances on these nodes to ground causes frequency response
peaking and possible circuit oscillations. General high-speed, signal-path layout
suggestions include:
- Continuous ground planes are
preferred for signal routing with matched impedance traces for longer runs.
However, open up both ground and power planes around the capacitive sensitive
input and output device pins. After the signal is sent into a resistor,
parasitic capacitance becomes more of a band-limiting issue and less of a
stability issue.
- Use good, high-frequency
decoupling capacitors (0.1μF) on the ground plane at the device power pins. For
best high-frequency decoupling, consider X2Y supply-decoupling capacitors that
offer a much higher self-resonance frequency over standard capacitors.
- When using differential signal
routing over any appreciable distance, use microstrip layout techniques with
matched impedance traces.
- The input summing junction is
very sensitive to parasitic capacitance. Connect any Rf, and Rg elements into
the summing junction with minimal trace length to the device pin side of the
resistor. The other side of these elements can have more trace length if needed
to the source or to ground.