Keithley 238 High-Current Source-Measure Unit

The Keithley 238 High-Current Source-Measure Unit is a four-in-one instrument that functions as a voltage source, voltage measure, current source, and current measure. It delivers precision sourcing and simultaneous measurement across a wide dynamic range, sourcing voltage while measuring current or sourcing current while measuring voltage. The 238 operates as a DC source, meter, sweep source, or full source-measure unit, making it suitable for semiconductor device characterization, leakage current measurement, and insulation resistance testing.

## Technical Specifications

**Source Capabilities**
• Voltage source ranges: 1.5V, 15V, 110V
• Current source range: 100fA to 1A
• Voltage source accuracy: ±(0.033% + 800µV) on 1.5V range; ±(0.033% + 2.7mV) on 15V range; ±(0.033% + 24mV) on 110V range
• Source noise: <3ppm (0.1–10 Hz bandwidth, except <20ppm on 1nA, 10nA, and 1A ranges)
• Source settling time: <500µs to 0.01% (10mA step, 10kΩ load)
• Source overshoot: 10¹⁴Ω paralleled by <20pF (1nA range)

**Measurement Capabilities**
• Voltage measurement range: 10µV to 110V
• Current measurement range: 10fA to 1A
• Voltage measure accuracy: ±(0.033% + 800µV) on 1.5V range; ±(0.033% + 2.7mV) on 15V range; ±(0.033% + 24mV) on 110V range
• Measurement sensitivity: 10fA current, 10µV voltage
• Measurement rate options: 416µs (4-digit), 4ms (5-digit), 16.67ms or 20ms (line cycle); maximum 1000 source/measurements per second
• Temperature coefficient: 50fA/°C

## Key Features

• Dual sourcing and measurement within single sweep
• Configurable measurement resolution (4 or 5 digits)
• Internal buffer supports 1ms per point acquisition
• Wide current dynamic range from femtoamps to amps
• High source output impedance enables precision voltage sourcing into low-impedance loads

## Typical Applications

• Semiconductor device I-V characterization
• Leakage current measurement
• Insulation resistance testing
• Component parameter extraction across wide signal ranges