Active & Differential Probes

Active and differential probes are specialized oscilloscope accessories designed to measure signals that cannot be safely or accurately captured with standard passive probes. Active probes use internal amplification circuitry to provide very high input impedance and low capacitive loading, minimizing circuit disturbance even at high frequencies. Differential probes measure the voltage between two non-ground-referenced nodes, making them essential for safely capturing floating signals such as those found in switching power supplies, motor drive gate circuits, and differential serial buses.

These probes are critical tools for power electronics engineers, EMC testing specialists, and R&D laboratories working with high-speed digital and analog circuits. Models from Hioki, Pico Technology, and Siglent span bandwidths from a few MHz up to several GHz, with high common-mode rejection ratios (CMRR) enabling precise differential measurements even in noisy environments.

Typical Applications

Switching power supply design — measuring gate drive signals and MOSFET switching waveforms referenced to floating nodes in half-bridge and full-bridge topologies
Motor drive and inverter testing — capturing differential voltage across phase windings and IGBT gate-emitter junctions
EMC pre-compliance testing — measuring conducted emissions and common-mode noise on power lines and cable harnesses
High-speed serial bus probing — capturing differential pairs such as USB, CAN, RS-485, and Ethernet with accurate common-mode rejection
Battery management system testing — measuring individual cell voltages in series-connected battery stacks

Popular Brands

Hioki offers wideband differential probes well-suited for power electronics and inverter applications. Pico Technology provides high-impedance active probes and active differential probes compatible with their PicoScope instrument range. Siglent's ADP series features adjustable attenuation ratios for flexible voltage-range coverage in both bench and field environments.