Apparatus and method for isolating and connecting two electrical circuits

Abstract

An inductor used to allow in-circuit and functional testing at the same point on a test system. An inductor is used having a saturated state wherein the inductor functions to connect the test system to the device under test wherein when a large direct current passes through the wires it generates a large magnetic field saturating the core of the inductor. Thereafter, small increases or decreases in the current passing through the wires are not affected by the core since the core is already saturated. The inductor also has a not saturated state when the inductor functions to isolate the test system from the device under test in functional testing. The inductor in the not saturated state functions to minimize current flow from the test system and wires to minimize loading effects of the test system on the device under test. In-circuit and functional testing can thereby both be performed on the same plane on testing equipment as a result of the inductor service to allow alternating states of impedence as required by alternating states of testing. The inductor functions as a switch which when closed connects the test system to the device under test for in-circuit testing and when open functions to decouple the testing system from the device under test. Use of the inductor to connect or decouple two circuits is disclosed. A method for connecting and decoupling two circuits and a method of connecting and decoupling a test system and a device under test are also disclosed.