High-Side Current Sensing Using Dual Current Mirrors — ZDS1009 Example
The ZDS1009 datasheet includes an interesting high-side current sensing schematic that uses two matched current mirrors to translate the voltage drop across a shunt resistor into a ground-referenced output current.
This implementation demonstrates an efficient analog method for high-side current measurement using only discrete transistors and resistors, leveraging precise current mirror matching for linear transfer characteristics.
A neat solution to implement on discrete transistors for high-side sensing applications (above 120 Vdc), where suitable differential amplifier ICs are rarely available.
Here is the LTSpice simulation of high side current sensing at power rail voltage 10V:
Here is the LTSpice simulation of high side current sensing at power rail voltage 100V:
