Vacuum Tubes: Before transistors were invented, vacuum tubes served a similar purpose in early electronics by amplifying or controlling electrical signals. However, they were bulky and less efficient compared to modern transistors.
Field-Effect Transistor (FET): A field-effect transistor is a type of transistor where current flow is controlled by an electric field rather than direct contact with other materials. FETs are widely used in many electronic applications due to their low power consumption.
Bipolar Junction Transistor (BJT): A bipolar junction transistor is another common type of transistor that uses both electron and hole currents for signal amplification or switching purposes. BJTs are commonly used in audio amplifiers and digital logic circuits.