The circuit are suited for high precision extended temperature service if V+ is reasonably constant since IZ is dependent on V+. R1, R2, R3, and R4 are chosen to provide the proper IZ for minimum T.C. and to minimize errors due to Ibias. The circuits shown should both be compensated for unitygain operation or, if large capacitive loads are expected, should be overcompensated. Output noise may be reduced in both circuits by bypassing the amplifier input. Here is a schematic drawing:
The circuits shown employ a single power supply, this requires that common mode range be considered in choosing an amplifier for these applications. If the common mode range requirements are in excess of the capability of the amplifier, two power supplies may be used. The LH101 may be used with a single power supply since the common mode range is from V+ to within approximately 2 volts of V-.
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