Input resistances of the single-input active-load differential amplifier

In a current mirror-loaded differential amplifier stage with bipolar transistors in low frequency, the resistances as seen from the inverting and noninverting inputs are different. This occurs although the circuit is perfectly balanced in currents, and identical transistors in the pair and the current mirror source are assumed. Simple expressions of the resistances from each input are obtained, which show a strong dependence on the Early voltage of the circuit devices.<
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