Brief

The 10x Probe

The name is very misleading. The 10x probe does not give you a gain of 10 between the signal at the tip on the device under test (DUT) and the input to the scope. Quite the opposite, it is really a 1/10th probe. It achieves this by adding a 9 Meg Ohm resistor in series with the tip and assuming the scope will be set for 1 Meg input. This is the 10:1 voltage divider at DC.

If this was all it did, the resulting bandwidth due to the low pass filter created by the high series resistance and the input capacitance of the cable and scope’s input capacitance would be less than 10 kHz. It would be totally worthless as a scope probe.

What enables the 10x probe to operate with a much higher bandwidth is a high pass filter in parallel with the low pass filter. By matching the pole frequencies of the low pass and high pass filters, the response of the 10x probe can be “equalized” over a high bandwidth, typically on the order of 100-500 MHz.