Selecting the Right SMU
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What is an SMU?
As its name implies, an SMU can force voltage or current and simultaneously measure voltage and/or current.
While all SMUs share this basic configuration, most SMUs have specific characteristics that aid them in achieving a given task. For example, SMUs designed for battery characterization only need to operate in two of the IV plane quadrants (positive voltage and plus or minus current), since the voltage across a battery is never negative. These types of SMUs typically have extremely accurate time-sampling capabilities coupled with the ability to collect data over long time periods (features necessary for precise battery drain analysis). In contrast, SMU designed for semiconductor device characterization must operate in all four quadrants of the IV plane (positive and negative voltage and plus or minus current), since semiconductor devices require characterization in both forward and reverse operation. These types of SMUs also need extremely precise low-current measurement resolution (down to the sub-femtoamp range), which necessitates guarded (triaxial) connectors rather than standard BNC connectors. Finally, for all types of SMUs it is important that they support remote (aka 4-wire or Kelvin) sensing to eliminate the effects of resistive voltage drop through the wires connecting them to the DUT.