Atetrode transistor is anytransistor having four active terminals.

There were two types of tetrode transistor developed in the early 1950s as an improvement over thepoint-contact transistor and the latergrown-junction transistor andalloy-junction transistor. Both offered much higher speed than earlier 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.^[1] It achieved its high speed by reducing the input to outputcapacitance. It became obsolete in the early 1960s with the development of thediffusion transistor.

• Dual-emitter transistor, used in two-inputtransistor–transistor logic gates
• Dual-collector transistor, used in two-outputintegrated injection logic gates
• Diffused planar silicon bipolar junction transistor,^[2] used in someintegrated 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 tetrode

• Multigate transistor
• Pentode transistor

• Some application aspects of the tetrode transistors PDF (point contact)
• The Tetrode Power Transistor PDF (alloy junction)
• TRANSISTOR MUSEUM Historic Transistor Photo GalleryWESTERN ELECTRIC 3N22 (grown junction)

• Transistor types

• Articles with short description
• Short description matches Wikidata