Download Performance of Regulated Supplies

Performance of Regulated Supplies
Definitions
Load Regulation
=
Change in VL from IL = 0 to full-load IL
Line Regulation
=
Change in VL from minimum VS to maximum VS
Output Resistance =
same idea as for an amplifier
Values for the simple circuit
The approach is based on feedback theory. This is the circuit:
Av is the differential-mode voltage gain of the op-amp, whilst ro is the output
resistance of the emitter follower without feedback (very low -- and the feedback
makes it lower still). From the non-inverting input of the op-amp onwards, we can
regard 'Av' as being the diff-mode voltage gain of the op-amp, whilst '' is the ratio
R2/(R1 + R2) by voltage division. So Av' = Av/(1 + Av), or approximately 1/, giving
1 + R1/R2. The input 'signal' voltage vs is already voltage-divided down by a ratio
rz/(R + rz), so any disturbance in Vs will be multiplied by (1 + R1/R2)[rz/(R + rz)]. The
line regulation is therefore the permitted range of Vs multiplied by this expression.
The output resistance is that of the emitter follower divided by (1 + Av) -- very low
indeed -- and the line regulation is the output resistance multiplied by the rated
maximum load current.