Q. How can I make high current or voltage measurements using HP4155/56 and UTMOST?

A. The HP4155/56 DC Analyzer can be configured with SMU and Pulse Generator expander box frame called HP41501A. The expander box can have different measurement unit options. The option unit for the expander box include GNDU (GrouND Unit), PGU (Pulse Generator Unit), MPSMU (Mid Power Source Monitoring Unit) and HPSMU (High Power Source Monitoring Unit).

In order to measure a device with currents higher than 100mA, the expander box with HPSMU and GNDU unit is required. The Power limit of the HPSMU is 20W (up to 200V or 1A) The Mid Power SMUs which are part of the main 4155/56 frame have power limit of 2W (up to 100V or 100mA). The HPSMU and GNDU units have both force and sense terminals. The GNDU unit can sink currents up to 1A and must be used with HPSMU for high current measurements.

In order to measure a bipolar device with collector current greater than 100mA the following hardware configuration is needed:

HPSMU Force connect to COLLECTOR

HPSMU Sense connect to COLLECTOR (optional)

MPSMU connect to BASE

GNDU Force connect to EMITTER

GNDU Sense connect to EMITTER

UTMOST SMU configuration screen supports the expander box unit configurations. The HP4155/56 main frame contains 4 MPSMUs therefore the 5th SMU is the HPSMU. The selection of “0” in the SMU configuration screen corresponds to “unused SMU”. Figure 1 demonstrates the UTMOST SMU configuration for the high current bipolar device measurement.