A positive current source (PCS) for supplying common mode current. The PCS includes a pair of unity gain inverting single ended amplifiers that are connected in antiparallel across a pair of matched resistors. Alternately, the resistors can be connected across the inverting and non-inverting sides of a differential amplifier. A constant voltage is applied across the resistors to supply the common mode current (I.sub.cm) while maintaining a common mode resistance of R/2 and a differential mode resistance approaching infinity. The PCS has a common mode resistance which is small enough to maintain a stable common mode operating point with process variations providing minimal impact.