Question
What are the advantages of Indirect Current Feedback?
Answer
1) Low power. ICF requires less active components than traditional
architectures.
2) Low cost. Trimmed thin-film resistors are not needed to set gain accuracy
and CMRR, saving manufacturing steps and therefore reducing end market cost.
3) No “hexagon plot” headroom limits. Page 1 of the AD8237 datasheet shows this
well. Unlike traditional AD620-style instrumentation amplifiers, ICF in-amps
can fully gain signals at the edge of their input range limits.
4) Better gain drift performance. External gain-setting resistors do not have
to match internal trimmed resistors over temperature. See gain drift
specification for AD620 or competitive part INA333.
5) High impedance REF pin. Adds flexibility and can save cost and power in many
cases. For example, if an op-amp is needed to drive the REF pin of a
traditional in-amp, that op-amp is typically not necessary for the same circuit
with the AD8237.