SLAAE49 February 2022 DAC43204 , DAC53004 , DAC53204 , DAC53204W , DAC63004 , DAC63204
The simulation shows the LED current vs the DAC output voltage. The base voltage needs to be 0.7 V less than the emitter voltage for a typical PNP-type BJTs to conduct. In this circuit, the chosen 2N2905 transistor starts conducting when the base voltge exceeds 900 mV.