Opamps general: current feedback CFB / voltage feedback VFB / input impedances

Document created by analog-archivist Employee on Feb 23, 2016
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Do all your opamps have high-Z (high-ohmic)inputs?


Most opamp have high-Z inputs. To be more precise, all voltage feedback
amplifiers have equal input impedances. At current feedback amplifiers the
input impedance of the inverting and non-inverting inputs are not equal, and
generally have unequal and uncorrelated input bias currents because the (+) and
(–) inputs have completely different architectures. The current feedback (CFB)
topology is primarily used where the ultimate in high bandwidth, high slew rate
and low distortion are required.

Here is an interesting document about "Choosing Between Voltage Feedback (VFB)
and Current Feedback (CFB) Op Amps":