Agilent Active Probe


I recently picked up a broken Agilent 1156A 1.5GHz active oscilloscope probe on eBay for cheap. This was a great opportunity to discover what is inside one of these probes.


The above picture is inside the main probe body that connects to the oscilloscope. It provides the power for the probe head and identification circuitry for when it is plugged into the scope. There is no signal conditioning done inside this case. The coax connector passes straight through and into BNC connector which normally sits in the recessed cutout on the left.


This next picture is the actual probe head. The amplifier is a bare die sitting just behind where the taper stops. It is wire bonded to the surrounding circuitry and is pretty much impossible to repair.

If the probe head is damaged consider the whole probe to be dead. It might be useful for parts on another older-but-working probe, but there isn’t much to be saved. However, if the probe body is damaged there is a good chance it is repairable!

There isn’t much more to explore on these probes without having a good microscope! If I have the chance to get better pictures of the front end I will add them to a new post. To close, here is another picture of the wire bonded probe head.