Unijunction transistor

<p>A unijunction transistor (UJT) is a three-lead <a href="/facts/Electronics/E4JhgISq">electronic</a> <a href="/facts/Semiconductor/zFf3mGTE">semiconductor</a> device with only one <a href="/facts/P-n_junction/CaKIdLPg">junction</a>. It acts exclusively as an <a href="/facts/Electronic_switch/V6mkIP2z">electrically controlled switch</a>.
</p><p>The UJT is not used as a linear amplifier. It is used in <a href="/facts/Electronic_oscillator/6NaXsSzJ">free-running oscillators</a>, synchronized or triggered oscillators, and pulse generation circuits at low to moderate frequencies (hundreds of kilohertz). It is widely used in the triggering circuits for <a href="/facts/Silicon_controlled_rectifier/ep3HLxmS">silicon controlled rectifiers</a>. In the 1960s, the low cost per unit, combined with its unique characteristic, warranted its use in a wide variety of applications like oscillators, pulse generators, saw-tooth generators, triggering circuits, phase control, timing circuits, and voltage- or current-regulated supplies. The original unijunction transistor types are now considered obsolete, but a later multi-layer device, the <a href="/facts/Programmable_unijunction_transistor/c93v7y7e">programmable unijunction transistor</a>, is still widely available.
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Unijunction transistor open-in-new

Unijunction transistor