Apparatus for minimizing optically and thermally induced noise in

Abstract

Method and apparatus for minimizing unpredictable sources of noise, or error voltages, at the microvolt level in precision analog components such as operational amplifiers is described. Sources of such error voltages are temperature gradients across the dice of the precision components enclosed in a hermetically sealed package, thermoelectric voltages caused by temperature differences between junctions of leads of the package with other metals, and light reflected from the substrate through the glass seals around the leads in the base of such packages. A skirted heat sink is positioned in thermal contact with the sides of the package which package is mounted on a substrate. The heat sink transfers heat from the heat sink to its ambient environment by radiation and convection to maintain the temperature within the package substantially constant. The skirt depending from the heat sink encloses the space between the base of the package and the surface of the substrate to form a substantially isothermal enclosure to maintain the temperature of the leads of the package substantially constant. The depending skirt also blocks, or absorbs, radiation from the ambient environment of the package which prevents such radiation from being transmitted through the seals of the package to minimize the production of photoelectric induced error voltages induced in photosensitive circuits of the component.