A common current pump made with in-amps uses a shunt resistor between the output of the in-amp and the REF pin. Typically, a buffer is needed to drive the REF pin in this application in order to preserve the common-mode rejection ratio. However, because the ICF topology results in a high-impedance REF pin, this can be simplified. This topology is much simpler and more efficient even than the traditional Howland Current pump and requires no matched resistors. Because the AD8420 and the AD8237 are both low power devices not designed to drive very heavy resistive loads, one or more external transistors can be used within the loop to boost the output current if necessary. This external output stage can be as simple as a single transistor or as complicated as the design requires. Some design considerations include sourcing and sinking ability, maximum output current level and thermal dissipation, crossover-distortion, short-circuit limits, and protection.