Reading Notes on the Good Book "Operational Amplifier Parameter Analysis and LTspice Application Simulation" 04-Current Detection and Amplification

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Reading Notes on the Good Book "Operational Amplifier Parameter Analysis and LTspice Application Simulation" 04-Current Detection and Amplification [Copy link]

In the chapter on dedicated amplifiers, the article introduces dedicated current detection amplifier circuits. In electronic products, current detection amplifiers are indispensable for power supplies, motors, battery-powered circuits, etc. There are two common detection amplifier methods, which are low-side current detection circuits, where the current detection resistor is connected in series to the ground (Figure 1), and high-side current detection circuits, where the current detection resistor is connected in series to the high voltage end (Figure 2).

Figure 1

Figure 2

The two methods have their own characteristics: the low-side current sensing method adds a sampling resistor in the ground loop, the low-side current sensing op amp uses the ground level as the reference level, and the current sensing resistor is connected to the non-inverting end. Although the low-side current sensing circuit is relatively simple, it will cause errors in the circuit signal, and the accuracy and power consumption of the current sensing resistor must also be considered.

These problems can be solved by using a high-side current-sensing circuit. The high-side current-sensing circuit is directly connected to the power supply end, and can detect any faults in the subsequent circuit and take corresponding protection measures. It is particularly suitable for various current detection applications. The high-side current-sensing method needs to handle large common-mode signals, and must distinguish a small detection voltage added to a high common-mode voltage.
This will be a complex design task, so for high-voltage, high-side measurements, dedicated high-side current-sensing amplifiers AD8418A are a better choice because they are designed to operate under high common-mode voltage conditions with superior accuracy. High accuracy can be achieved over a wide common-mode range. Some students may say, "This op amp is too expensive! I can design a similar circuit with an ordinary op amp." - Great! Please tell me, I really want to learn, thank you in advance!

Jacktang

Commonly used methods: low-side current sensing circuit and high-side current sensing circuit

Yes