BJT Active Battery (Floating Active Level Shifter)

The circuit buffers the input current and maintains a voltage difference (Vbatt) between the source and the load. The voltage difference is the sum of Vbe1, Vbe2, and the voltage drop across Rvadj. The current through Rvadj is set through Ribset. The SPDT switch swaps the LED and 5 kΩ resistor to verify the level shifting functionality of the circuit as described in the first sentence, even with varying load characteristic. The voltage difference can be made approximately constant by keeping the sum of Vbe1 and the voltage drop across Rvadj large relative to Vbe2. This can be done by increasing the bias current and/or the resistance of Rvadj.