Laser-trimmable digital resistor

Abstract

A laser system and method for cleanly trimming or severing resistive links fabricated on in undoped gallium arsenide substrate without damaging or affecting adjacent circuit structures or the underlying or surrounding substrate is disclosed. The system includes a laser source adapted to generate an output at a wavelength within the range of 0.9 to 1.5 μm, a resistive film structure formed on an undoped gallium arsenide substrate, and a beam positioner and alignment system to align the laser source with the target structure. The method includes generating a laser output at a wavelength in a range of about 0.9 to 1.5 μm and directing the laser output to illuminate a resistive thin-film structure fabricated on a gallium arsenide substrate. The resistive film structure includes a first layer of protective dielectric and a layer of resistive thin-film material. Preferably, a second layer of protective dielectric lies upon the layer of resistive thin-film material. Further, there is disclosed a resistive trim network suitable for use with a bias circuit for a power amplifier that requires a quiescent current of 130 mA. The trim network includes eleven thin-film resistors arranged in an asymmetrical array of series resistors, parallel resistors, and tying resistors.

Dependencies are inferred from the claim text.