The key function test (KFT), is a dynamic test method, also known as the main function of the overall function test or inspection. Refers to the specific working conditions (ie normal use the device environment, usually at room temperature), without considering the limits of the device parameters (such as maximum / minimum parameter) for normal operation of the state, for the necessary test logic or signal status. This test is based on original specifications, application notes, or client application site, as well as industry standards or specifications, design feasibility test vectors or special test circuit, the test sample to impose appropriate and effective incentives (signal) input through the external circuit adjustment control, such as signal amplification, or convert match the specific conditions, analysis of the output signal of the logic of relations and the changing state of the waveform, detection device features.

This is a relatively quick and low-cost test methods to meet the device requirements of conventional application circuit.