Transmission line probe

PP066-7.5GHz low capacitance impedance passive probe, 500/1K Ohms

Transmission line probe is a special passive probe suitable for high-frequency measurement. It is not like a traditional passive probe with high impedance, but has a precise transmission line built in to match the 50 ohm impedance of the oscilloscope. This makes the input capacitance much smaller than 1pF, minimizing the load effect on high-frequency signals. The matching network at the front end of the probe improves the DC input impedance, which is lower than traditional passive probes (usually 500ohm to 5Kohm), but can remain constant throughout the entire frequency band. A traditional 10 fold attenuation passive probe has a 10Mohm DC impedance, but the impedance drops sharply with increasing frequency, lower than the impedance of transmission line probes below 100MHz.

Under certain application conditions, transmission line probes have advantages over active probes. In addition to being cheaper, its passive characteristics make it more resistant to high voltage and static electricity. Transmission line probes are suitable for measuring fast edge narrow pulses with amplitudes exceeding the dynamic range of active probes, and the parasitic effects of frequency response tend to be less. When the frequency response of active probes is questioned, a sampling oscilloscope paired with a high bandwidth transmission line probe will be a gold standard.