Active differential probe with ultra-low input capacitance

Abstract

The invention provides an active differential probe with ultra-low input capacitance, which comprises two probe input terminals and a differential probe amplification module with double input ends, wherein a damping resistor and an RC (resistor-capacitor) parallel circuit are connected between each probe input terminal and one input end of the differential probe amplification module in series; each RC parallel circuit is formed by connecting an input resistor to an input capacitor in parallel; the input resistors and the input capacitors are arranged on insulation substrates; each input capacitor is a micro-strip interdigital capacitor and is formed by top layer copper foil of each insulation substrate; each input resistor is connected between a first via hole and a second via hole, and mounted at a position, opposite to each micro-strip interdigital capacitor, on a bottom layer of each insulation substrate. According to the probe, the micro-strip interdigital capacitors serve as the input capacitors, so that the ultra-low input capacitance of the probe is realized, and the consistency of the two input capacitors is ensured.

Description

technical field [0001] The invention relates to the technical field of measurement and testing, in particular to an active differential probe, more particularly to an active differential probe with ultra-low input capacitance. Background technique [0002] In the field of test and measurement, the probe is a device used to connect the circuit under test and the measuring instrument, collect the signal under test and transmit it to the measuring instrument. The probe needs to be able to detect signals without distortion within its frequency band and not adversely affect the circuit or signal under test. This requires the probe to have a larger input resistance and a smaller input capacitance. High input resistance and small input capacitance can separate a small current from the circuit under test and reduce the impact on the circuit under test. The input resistance needs to be higher than the measured circuit. The resistance of the test circuit itself is much larger, and th...

AI Technical Summary

Problems solved by technology

Since the capacitors C1P and C1N are very small, generally less than 1pF, they are implemented with chip capacitors. Even if the existing high-precision and high-Q capacitors on the market are used, the highest precision A range can only achieve ±0.05pF due to the limitation of the device itself. It is difficult to achieve the consistency of the two input capacitances when the parasitic capacitance is always present

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