Tips and Techniques for Efficient DC Testing and Current-Voltage Characterization
This e-guide explores some of the most common DC current vs. voltage (I-V) tests being performed today, the seemingly inherent complications posed by each, and how new techniques can help to not only overcome these challenges but enhance efficiency and productivity, as well.
Topics covered include:
- I-V Characterization of Two-Terminal Devices
The current-voltage (I-V) characteristic of a two-terminal device is defined as the relationship of the current through the device and the voltage across its terminals. I-V characterization is routinely performed in research and development on a variety of electronic two-terminal devices, including resistors, diodes, LEDs, solar cells, and sensors. I-V characterization of two-terminal devices involves stepping the voltage level across a device or the current level through a device from one level to another and measuring the resulting currents or voltages in an operation that is known as a sweep. The data collected is plotted with voltage on the X-axis and the current on the Y-axis to produce the characteristic I-V curve.
- Characterizing the I-V Parameters of Three-Terminal Devices
Characterizing the I-V parameters of three-terminal devices, like MOSFETs is crucial to ensuring proper operation in the intended application and in meeting specifications. Some of these I-V tests include gate leakage, breakdown voltage, threshold voltage, transfer characteristics, drain current, and ONresistance. Though this process shares many similarities with two-terminal-device I-V characterization, with three-terminal electronic components, the current-voltage relationship at one pair of terminals is dependent on the current or voltage on a third terminal. The data from each sweep is plotted on a complex current-voltage graph with multiple curves, each curve representing the current-voltage relationship of the terminal pair at a different value of current or voltage on the third terminal.
- Measuring Resistance - Configuring an Instrument to Properly Display Results
Resistance is the measure of a material’s opposition to the flow of electricity and its measurement is specified in the unit of Ohms. Resistance measurements are typically performed by sourcing a known current level through a device, measuring the resulting voltage across its terminals, then using Ohms Law to calculate the resistance. This is the method used most often by the resistance measurement functions of digital multimeters (DMMs) and source measure unit (SMU) instruments to measure resistance.
- Device Power and Efficiency Measurements
Greener, more efficient semiconductor devices, integrated circuits, and power systems require testing to evaluate parameters such as maximum power, battery discharge rates, power efficiency vs. current, or device off-state current. Power is a calculated measurement and requires measuring the voltage across the device, as well as the current through the device. The voltage measurement is then multiplied by the current measurement to calculate the power. Efficiency is the ratio of power drawn out of a device to the power sourced in to the device.
- DC Power Consumption Analysis for Low Power Products
Characterizing a power usage profile is essential for low power devices, such as Internet of things (IoT,) portable wireless, wearable, portable and implantable medical, and low power industrial products. Power usage directly correlates with battery drain and impacts product usefulness. DC Power analysis is a non-trivial task, since these devices often draw current in wide ranges from nano-amps to amps depending on operating modes and often have short wake up times, as well, tthat can last for as little as a few microseconds and require extensive data logging periods to capture a complete power usage profile.
- Characterizing Load Current Waveforms and Transient Behavior
Most electronic systems contain analog circuits, microprocessors, DSPs, ASICs, and/or FPGAs that require multiple supply voltages. To ensure reliable and repeatable operation of these systems, transient behaviors, such as power-up and power-down timing, ramp rates, and the magnitude of different supply voltages must be appropriately controlled. Voltage and current sizing, monitoring, sequencing, and tracking are essential for characterizing the transient performance of power supplies.