Esd Protection At The Probe Tip - Keysight 85024A User's And Service Manual

Service 7

ESD protection at the probe tip

The FET integrated circuit amplifier is located at the tip of the probe. The FET
input of the amplifier is protected by a bidirectional voltage limiter as shown in
Figure 7-1.
Figure 7-1 Probe tip input circuit
The voltage limiter element has a negligible effect on circuit operation for input
voltages within specification. The voltage limiter is a non-linear element: it begins
to conduct current at about 2.5 volts. It effectively limits voltages at the amplifier
input to less than ±4 volts. This prevents amplifier damage from low levels of ESD.
Even with the protection provided by the voltage limiter element, the probe is still
sensitive to ESD. High levels of ESD can cause permanent damage to the voltage
limiter element itself. Careful ESD precautions must be observed when using the
probe.
Keysight 85024A User's and Service Guide 59