Performance limitations of low-voltage regulators using only n-p-n transistors

Techniques to reduce the sensitivity of the error amplifier to supply voltage and temperature variations in low-voltage regulators which use only n-p-n transistors as active devices are examined. The line regulation for inherently stable error amplifier topologies is bounded below by 0.7 mV/V. Current or voltage sharing imposes a constraint on the gain available from the feedback error amplifier. This has not been previously achieved with n-p-n or BiCMOS circuits. A fully compensated all-n-p-n regulator that achieves the optical performance using feedforward internal bias stabilization is described. The factors degrading line regulation are examined