SBOS070D October 1997 – December 2019 OPA548
A programmable source or sink power supply can easily be built using the OPA548. Both the output voltage and output current are user-controlled. See Figure 30 for a circuit using potentiometers to adjust the output voltage and current while Figure 31 uses DACs. An LED tied to the E/S pin through a logic gate indicates if the OPA548 is in thermal shutdown.
Figure 30 illustrates how to use the OPA548 to provide an accurate voltage source with only three external resistors. First, the current limit resistor, RCL, is chosen according to the desired output current. The resulting voltage at the ILIM pin is constant and stable over temperature. This voltage, VCL, is connected to the noninverting input of the operational amplifier and used as a voltage reference, thus eliminating the need for an external reference. The feedback resistors are selected to gain VCL to the desired output voltage level.