Passive probes slash input capacitance - Embedded.com

Passive probes slash input capacitance

Tektronix has developed the TPP1000 and TPP0500 passive voltage probes to provide high input dynamic range, robust mechanical design and lower cost – with performance similar to an active probe.

The probes can be used with the MSO/DPO5000 series of mixed signal oscilloscopes as well as the MSO/DPO4000B series.

Mark Briscoe, Product Marketing Manager for the Midrange Scope Product Line at Tektronix said, “When we talk to customers the number one issue they have asked us to help with is to reduce the impact of the probing of their system. That usually comes in the form of capacitive loading which is traditionally the downside of passive voltage probes. It has effects and can make a circuit work or not work. They want us to minimize that impact.”

Tektronix says competitive passive voltage probes have at least 9.5 pF input capacitance.  The TPP1000 passive probes also deliver 1 GHz of bandwidth compared with a maximum of 500 MHz bandwidth on existing probes.With twice the bandwidth and half the capacitive loading, the TPP Series probes deliver more accurate signal capture. 

The passive voltage probes have a 10 MΩ input resistance to limit the effect on circuits with capacitive loading of 3.9 pF at the probe tip. The probes have a 300V  dynamic range.

“The oscilloscopes contain an ASIC developed by Tektronix which is basically the front end receiver and that talks to the probe and they are electrically matched together so that the probes can only be used with scopes that have the ASIC,” said Briscoe.

Typically passive probes have to adjusted manually for low frequency compensation but the TPP1000 and TPP0500 probes automatically do a full bandwidth – low and high frequency – calibration with the oscilloscope. “By pushing a button on the scope automatically does the calibration is around 4s. Usually high frequency calibration means the unit has to be returned to factory for adjustment. The ASIC design removes that need and the scope remembers individual probes to avoid re-calibration. The days of having to use a screwdriver to manually adjust the probes are gone,” said Briscoe.

The probe also has a key tab that restricts which oscilloscopes the probes can be plugged into.

The probes are provided as standard with every MSO/DPO5000 and MSO/DPO4000B series oscilloscopes with additional TPP1000 and TPP0500 probes available for $885 and $585
respectively.

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