  On-silicon inductors using a bulk 0.18 {\mu}m CMOS process have been
designed. By shunting different metal layers in parallel, inductor values and
quality factors were simulated. Selected inductors were then employed in two
open-loop buck converters for comparison: the first used an off-chip discrete
diode, and the second used an on-chip active diode. All inductors and
converters were sent for fabrication. The fabricated inductors were then
measured to have values more than 250 nH over a wide range of frequency,
validating the simulation results. The buck converters were switched at 30 MHz
with a fixed duty ratio of 0.5, to generate an output voltage of 1.2 V from an
input voltage of 2.4 V. The peak efficiency was measured to be 69.1% for a
light load current of 12.9 mA.
