A DAQ board is outputting 0-10VDC analog voltage via its DAC. The DAC cannot supply more than 5mA so I'm planning to use the following emitter follower for more current(x-axis is the DAC outpout voltage incresing 0 to 10V, y-axis is the base emitter voltage difference):
I thought emitter follower keeps the difference between the base voltage and emitter voltage constant around 700mV.
But if I use the following resistor 1ohm, the emitter follower cannot function anymore and will draw hundreds of mA current from DAC which may cause its damage. Here is the 1ohm case:
If I setup with the right resistor as in the first figure I'm safe but if someone accidentally shorts the resistor or ect. I dont want the DAC to be damaged.
I have two questions:
1-) Why emitter follower cannot keep the base emitter voltage constant in 1ohm case?
2-) Is there a way to totally be safe for DAC will never get loaded?