How to Perform Synchronized FET Measurements

+ Pro Benchtop Source Measure Unit

Synchronize Gate And Drain Measurements

A synchronized Field-Effect Transistor (FET) measurement uses two coordinated Source Measure Unit channels to control the electrical conditions at the gate and drain of a FET while acquiring current measurements at corresponding voltage points. For a typical FET Id-Vg measurement, one channel is assigned to the gate and a second channel is assigned to the drain. The gate channel sources a voltage sweep while measuring current, and the drain channel establishes the required drain voltage while measuring drain current. Both channels operate together so that measurements are acquired under coordinated gate and drain conditions. In the demonstrated configuration, Channel 1 is connected to the FET gate and configured for voltage sourcing with a gate current compliance limit of 1 µA. Its voltage is swept linearly from 0 V to 2 V using 101 points, producing 20 mV voltage increments. Channel 2 is connected to the drain and configured to maintain 2 V across the same 101 measurement points, with its current compliance set to 100 mA. High Force and Low Force connections provide the electrical paths between the two measurement channels and the device under test. The resulting FET IV characterization records the drain-current response as the gate voltage changes, allowing gate voltage to be plotted against drain current as a transfer characteristic. The measurement can therefore coordinate voltage sourcing and current acquisition without requiring independently programmed voltage sources and current meters.

Synchronization can also be controlled through the triggering parameters of the two measurement channels. The demonstrated transistor characterization procedure initially uses the automatic trigger mode and then shows how both channels can be configured for synchronous triggering. For the synchronized configuration, the trigger type on Channel 1 and Channel 2 is changed to SYNC. The source trigger count and measurement trigger count are each configured to 101, corresponding to the 101 sweep points used in the measurement. The application note specifies that the source and measurement trigger counts should equal the number of sweep points. A measurement trigger delay of 100 ms is then applied to both channels, demonstrating how acquisition timing can be controlled relative to each measurement point. Measurement speed and range can also be adjusted as part of the synchronized measurement setup. The documented procedure shows NORMAL measurement speed, corresponding to an aperture time of one power line cycle, as well as automatic current-range operation and an example using a 10 nA minimum current measurement range. After the two channels are configured, both output relays are enabled and the synchronized sweep is triggered. The resulting FET Id-Vg measurement can be displayed directly in Graph View, where gate voltage is selected for the X-axis and measured drain current forms the transfer characteristic. Linear or logarithmic Y-axis scaling can be selected for viewing different current regions, while the individual FET IV characterization measurement points can also be reviewed through the measurement-result list.

Synchronized FET Measurement Solution

Performing synchronized FET measurements requires two coordinated voltage-source and current-measurement channels that can apply gate and drain conditions while acquiring measurements at corresponding points. The Keysight dual-channel precision Source Measure Units (SMUs) provide two channels with independent IV measurement capability and the ability to supply constant or swept voltage and current, enabling the gate and drain of a three-terminal FET to be controlled from a single instrument. For a synchronized FET measurement, Channel 1 can apply the gate-voltage sweep while Channel 2 maintains the drain bias. Independent compliance settings restrict the output on each channel, while synchronized trigger settings coordinate sourcing and measurement. The demonstrated FET Id-Vg measurement uses 101 measurement points on each channel and shows how SYNC triggering can be configured with equal source and measurement trigger counts and a 100 ms measurement trigger delay. Measurement speed and current-range operation can also be configured to match the required transistor characterization conditions. The front-panel graphical user interface supports the complete FET IV characterization workflow without requiring a test program. Single View enables each channel's source and measurement conditions to be configured independently, while Graph View displays the resulting IV curve. Measurement results can also be inspected as a data list. The application note additionally documents PathWave BenchVue, PathWave IV Curve software, and EasyEXPERT group+ as software-control options for PC-based measurement workflows.

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How to Perform Synchronized FET Measurements

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