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I was told some oscilloscopes have 50 ohm impedance settings for radio frequency measurements for impedance matching (as opposed to one 1M ohm resistor and a 10pF capacitor in parallel for load impedance, which is good for low frequency measurements). I was able to find a circuit schematic of an oscilloscope. for the usual 1M ohm and 10pF capacitor in parallel. But i haven't been able to find a circuit diagram for the 50 ohm impedance oscilloscope. Id lile to know what the oscilloscope circuit looks like for the rf 50ohm impedance settings

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  • \$\begingroup\$ It would just a RF reed relay and 50 Ohms . But you can add a BNC T and a 50 Ohm R or BNC 50 Ohm terminator for 1:1 measurements \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 19 '18 at 23:37
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There are many sources on the subject, you need to search for something like "1 GHz PC scope". Many IC manufacturers offer amplifiers that can work only with 50-Ohm sources and loads. In fact, it is very difficult to get GHz-range with 1 MOhm input.

Here is an example, a reference design from Texas Instruments, "50-Ohm Oscilloscope Front-end Design Guide" . It looks like this:

enter image description here

All components are commercially available, and good luck.

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