There is a high-bandwidth amplifier on the front end of the active probe. The amplifier needs power supply, and the name of active probe attribute to it. The input impedance of the amplifier is relatively higher, so the active probe can provide a relatively higher input impedance; while the amplifier output drive capability is very strong, so it can directly drive the rear 50 ohm load and transmission line. Because the 50-ohm transmission line can provide a high transmission bandwidth, plus the high bandwidth of the amplifier itself, so the entire probe system compared to passive probes can provide higher bandwidth.
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