This part is a kind of semiconductor called EL5191C.

Function of this product has 1GHz Current Feedback Amplifier.

Manufacturers : Elantec Semiconductor

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Some of the text within the PDF file :

EL5191C EL5191C 1GHz Current Feedback Amplifier Features • 1GHz -3dB bandwidth • 9mA supply current • Single and dual supply operation, from 5V to 10V supply span • Available in 5-pin SOT23 package • High speed, 600MHz product available (EL5192C, EL5292C, and EL5392C) • Lower power, 300MHz product available (EL5193C, EL5293C, EL5393C) General Description The EL5191C amplifier is of the current feedback variety and exhibits a very high bandwidth of 1GHz. This makes this amplifier ideal for today’s high speed video and monitor applications, as well as a number of RF and IF frequency designs. With a supply current of just 9mA and the ability to run from a single supply voltage from 5V to 10V, these amplifiers offer very high performance for little power consumption. For appli [ ... ]

EL5191C PDF Datasheet Download