Since BJT transistors function using variations of current (and in turn, acts as a current-limiting device, hence the name "transistor", a contraction of "transfer resistance") I wanted to see what it would take to provide the correct current-limiting conditions to drive multiple LEDs. I have a batch of 2n3904's at home, which, according to the datasheet, can pass a maximum collector current of 200mA, which gives us 10 LEDs in parallel passing 20mA each.
Do realize that this is a simulator and real-world conditions can yield vastly different results, so don't be upset when you fry any components. Experiment, break things, and have fun.
