An optical amplifier includes a passive waveguide region and an active waveguide region. The drives require less maintenance, result in less wear, are highly accurate, can operate at high speeds and at high loads, and are easily programmable. The memory system is provided a spare memory bank. The switched variable and reference capacitors are employed in conjunction with the A-to-D converter to perform, at the common node, a plurality of direct voltage measurements for use in generating an expression defining the capacitance of the variable capacitor.