Low Drop, High-Side Sense Current Limiter Adjusts to Zero 2018-03-08

The common two-transistor current limit circuit uses the base-emitter voltage of a BJT as a reference voltage across a series sense resistor to set the current limit. This gives a voltage drop of near 0.7V at the current-limit point.
It is desirable to have as low a drop as possible, to allow a maximum output voltage, and to limit the power dissipated in the sense resistor at high current limit settings.
For example, a 2A limit generates a maximum dissipation of about 1.4W in the sense...

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