New Current Source And Measurement Techniques

Currents up to 100A required May Be In A Wide variety of high-power device characterization applications. High test currents Could Be Needed for Such devices have insulated gate transistors (IGBTs), MOSFETs, RF power transistors, high-brightness LEDs, solar cell arrays, and power management devices. There Are Two Problems Associated with this type of testing: (1) Finding a single DC power supply Cdn That Deliver The required current, and (2) Avoiding excessive device temperatures When Applying Such high currents. The latter "IS Usually Accomplished by Applying Relatively high currents as short pulses. This means specified in the power source capable of Must Be pulse mode operation up to The Peak Needed For the current test. Finding a DC power supply specifications thesis With May Not Be Easy.

A pulsed source IS Often essential for testing a high power device Because DC current gain Would Skew The Resistance Of The device under test (DUT) due to Joule heating. DC current sources Typically you do not let Their pulse outputs. Although high-power pulse generators are available, They Have No built-in measurement capabilities, So They require Synchronizing The Operation Of A Separate ammeter With The pulsed test signal. Their cost and Complexities In The test set-up tends to make expensive pulse testing. Still, You Can Create an Economical pulsed DC current source appropriée Yourself With The source-measure unit (SMU), Even If Its maximum output current spécifié Does not Quite Reach The level needed.

Pulsed sweeps for Higher Power. With The Right EMS features, You Can substitute a pulsed sweep for a DC sweep to Obtain Higher Power I-V Cure With little detriment to your device characterization results. However, You Must Recognize That Some testing DUTs (Such as capacitors) With pulsed sweeps May not adequately correlate With DC sweeps. This Is due to large displacement currents generated That Can Be At The Sharp Edge of the voltage pulse, Which May Chang thesis devices' electrical properties. On the Other hand, pulsed I-V testing IS essential for Other device types, Such as RF power amplifiers or Even low-power nanoscale devices, to Obtain optimal results.

Düring high-power continuous wave DC testing, semiconductor material In The DUT Will start to dissipate heat as Applied Power. As The OTC heats up, conduction current DECREASE Because The semiconductor charge carriers HAVE MORE Collision With The vibrating lattice (ie, phonon scattering). Therefor, The Will Be Measured current erroneously low due to self-heating effects. Given That thesis types of devices Typically run in pulsed mode (Intermittently Rather Than sécurité), The erroneously low current DC measurements accurately Will not Reflect Their normal performance. In These Circumstances, pulsed testing Must Be used.

You must take two Factors Into Account When Changing from a DC sweep to a pulsed sweep. The wide pulse Must Be Sufficient Enough To allow time for transient conditions Within The DUT, cabling, and Other interfacing circuitry to settle out. Allow this measurement instruments to take stable, repeatable Readings. At The Same Time, however, The Pulse Can not Be so wide That It Exceeds The test instrument's maximum pulse width and duty cycle limits, Which Would Violate The instrument's power Allowed duty cycle. That pulses are too wide Cdn aussi create The Same device self-heating Problems That Occur With Canon DC sweeps.

Combining multiple channels to Achieve Higher SMU DC current. Using a dual-channel SMU (or Two Separate SMUs) You May Be Able to Get the Test Needed by Combining The current outputs from Two channels. The MOST common way of doing this Is To Connect The current sources (channels) in parallel Across the DUT. This test setup Takes Advantage Of A Well-Known electrical principle "(Kirchhoff's current law), That Which states Two current sources connected to circuit node in the Same Will Have Their parallel currents Added together. In thi.