Tetrode transistor

Early tetrode transistors

• Point-contact transistor having two emitters. It became obsolete in the middle 1950s.
• Modified grown junction transistor or alloy junction transistor having two connections at opposite ends of the base. It achieved its high speed by reducing the input to output capacitance. It became obsolete in the early 1960s with the development of the diffusion transistor.

  Modern tetrode transistors

• Dual emitter transistor, used in two input transistor-transistor logic gates.
• Dual collector transistor, used in two output integrated injection logic gates.
• Diffused planar silicon bipolar junction transistor, used in some integrated circuits. This transistor, apart from the three electrodes, emitter, base and collector, has a fourth electrode or grid made of conducting material placed near the emitter-base junction from which it is insulated by a silica layer.
• Field effect tetrodes