What are the advantages and disadvantages of active single-ended probes?

　　Oscilloscope probes are critical to the accuracy and correctness of your measurement results. It is the electronic component that connects the circuit under test to the input of the oscilloscope. The simplest probe is a wire connecting the circuit under test and the input end of the electronic oscilloscope, while complex probes are composed of resistive and capacitive components and active devices. Without shielding measures, simple probes are susceptible to interference from external electromagnetic fields. Their equivalent capacitance is large, which increases the load of the circuit under test and distorts the measured signal. In this article, PRBTEK will introduce active single-ended probes to you.

　　Active single-ended probe principle

　　Active single-ended probes generally have high impedance (around 1MΩ) and low parasitic capacitance. There is a high-bandwidth amplifier at the front end, and the power supply of the active probe is mainly used for this amplifier. The amplifier drive signal reaches the oscilloscope through a 50Ω transmission line, and the input impedance of the oscilloscope needs to be selected to be 50Ω for matching. Due to its lower parasitic capacitance and 50 ohm transmission, active single-ended probes can provide higher bandwidth than passive probes and are therefore mainly used in the measurement of high-frequency signals.

　　Active single-ended probe schematic

　　Advantages and disadvantages of active single-ended probes

　　Advantages and disadvantages often go hand in hand, and the same goes for active single-ended probes. Being able to measure signals with higher bandwidth is its advantage, but due to the need to integrate an active amplifier, its cost is higher than that of passive probes. An active single-ended probe with a bandwidth of several GHz can cost tens of thousands of yuan. In addition, since the signal input range of the high-bandwidth amplifier is very limited, its dynamic range is limited. Generally, the dynamic range of active single-ended probes is only within a few volts, and the maximum voltage that the probe can withstand is only tens of volts. Volt. Active single-ended probes can also be used in the measurement environment of low-impedance high-frequency signals, and because their input impedance is higher than passive transmission line probes, their loading effect is smaller. Not only that, the R&S active single-ended probe can also be connected to the RT-ZA9 (N-type conversion connector, USB power supply) accessory, and then used on RF signal sources and spectrum analyzers to test signals in special environments, such as traditional 50 ohm coaxial cable cannot be connected to the detection point, or when it is necessary to use a high-impedance probe to detect the signal spectrum of the point to be measured.