Instructions: In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Input: What is necessary for the transistors to work?, Context: There are two types of transistors, which have slight differences in how they are used in a circuit. A bipolar transistor has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain.
Output:
A small current