TIPD101, Low-Side V-I Converter Reference Design, 0 to 5 V Input, 0 mA to 500 mA Output

TIPD101, provides theory, component selection, simulation, PCB design, and measurement details for a low-side voltage-to-current (V-I) converter. The circuit delivers a well-regulated current to a floating load which could include actuators, sensors, motors, LEDs, and many other applications. The design uses the OPA735 small-signal Op-Amp to control an NPN emitter-follower that sources current to the load. The current is accurately regulated by feeding back the voltage drop across a low-side current-sense resistor to the Op-Amp. The rail-to-rail input/output topology of the OPA735 allows for good accuracy even at low currents because there is very little (dead-zone) in either the input or output stage