OperatingBasics
P7225 2.5 GHz 10X Active Probe UserManua l 23
Vsource
ProbeC in
≤0.8pF
Lgl(ground lead)
Figure 7: Ground lead equivalent circuit
Ringing andrise time degradation can be masked if the frequency
content of the signal degradation is beyond the ba ndwidth of the host
instrument.
Youcan det ermine if ground lead effects may be a problem in your
application if you know the self-inductance (L ) and capacitance (C)
of your probe and ground lead. Calculate the approximate resonant
frequency (f0) at which this parasiticcircuit will resonate with the
following formula:
f0=1
2πLC
The preceding equationshows that reducing the ground lead
inductance will raise the resonant frequency. If your measurements
are affected by ringing, lower the inductance of your ground path
until the resultingresonant frequency is well above the frequency of
your measurements.
The low-inductance ground pogo pin described in Feat uresand
Accessories starting o n page 5 can help you reduce the effects of
ground lead inductance on your measurements.