US 3,979,672 AGranted

Transistor testing circuit

AssigneeRCA Corporation

InventorHugh Arnoldi

Life of this patent

Estimating the term…

Loading patent…

Abstract

An automated test set for determining the reverse biased second breakdown characteristics of a bipolar transistor without destroying or degrading the transistor under test (TUT). A source supplies current to the TUT through an inductor. The amplitude of this current increases in predetermined increments. After each current amplitude increase, the base-emitter junction of the TUT is reverse biased and the source is disabled. If enough energy is stored by the inductor to cause second breakdown, this breakdown is detected and the test is terminated. Otherwise, the test continues until the test current reaches a predetermined maximum amplitude, at which time the test is terminated. Damage to the TUT is avoided by restricting the stored energy to levels high enough to cause second breakdown but low enough that the remaining energy does not cause thermal damage.

Claims12

Dependent claims

A test circuit for a bipolar transistor, said transistor having collector and emitter electrodes defining a conduction path therebetween and a control electrode comprising, in combination:

energy storage means connected in series with said path to form a series circuit;
means for applying successively larger currents to said series circuit;
means for applying a forward bias to said control electrode while applying said successively larger currents;
means, after each application of a current to said series circuit, for concurrently interrupting the flow of said current and changing the bias applied to said control electrode from a forward to a reverse bias;
means responsive to the voltage across said energy storage means when said current is interrupted for providing a low impedance path across said series circuit in a direction to permit current flow from said energy storage means through said conduction path and said low impedance path back to said energy storage means;
and
means for indicating a rapid decrease in the voltage between the collector and emitter electrodes of said transistor while said reverse bias is present.

4 more elements

Apparatus for testing a bipolar transistor, said transistor having a control electrode, and collector and emitter electrodes defining a main conduction path therebetween, for reverse biased voltage second breakdown comprising, in combination:

an inductance coupled to said conduction path forming a series path therewith;
means for supplying a current to said series path, whose amplitude increases in predetermined increments;
means for rendering said transistor nonconductive by concurrently changing the control electrode bias from a forward to a reverse bias and for disabling said means for supplying a current at a predetermined time after each current amplitude increase until said breakdown occurs, said breakdown being manifested by a rapid decrease in the potential across said conduction path;
an asymmetrically conducting element coupled across said series path, said element presenting a relatively high impedance to current flowing from said means for supplying a current and a relatively low impedance to current flowing through said series path when said breakdown occurs;
and
means for detecting said rapid decrease in the potential.

3 more elements

Dependencies are inferred from the claim text.