Controlling Transistors
You seem to have mixed up several things you read about.  In a broad sense, there are two types of transistors, called BJT (bipolar junction transistor) and FET (field effect transistor).  Nowadays, computers are made from the FETs.  These are controlled by a voltage, not a current.  The voltage produced by the output of one logic gate is applied to other logic gates.  Internally the inputs of these logic gates are the gates of the FET transistors.  Note that "gate" as in "logic gate" is different from "gate" as one of the terminals of a FET.