Transistors in darlington conguration

The Darlington circuit contains two connected transistors. Operation can be described by a cascade, wherein the rst transistor serves as a preamplier of the second transistor. The achieved gain is approximately the product of the two individual gains of the transistors used. To let the yellow LED light up, only a few microampere into base are needed. The achieved current amplication is that high, that applying a ngertip at the seperately crossed-brick is enough to get a current ow through 100 kOhm resistor into the base to let the LED light up. You do not need to worry about your health, because the current is not noticeable.