NXP Semiconductors Unijunction Transistors (UFT) 0
| Part | RoHS | Manufacturer | Configuration | Surface Mount | Maximum Power Dissipation (Abs) | Package Body Material | Transistor Application | Maximum Emitter Current | Terminal Form | Package Shape | No. of Elements | Maximum Inter-base Voltage | No. of Terminals | Package Style (Meter) | Sub-Category | Maximum Operating Temperature | Transistor Element Material | Minimum Operating Temperature | Terminal Finish | Minimum Intrinsic Stand-off Ratio | Maximum Static Inter-Base Resistance | Terminal Position | JESD-30 Code | Case Connection | Qualification | Maximum Intrinsic Stand-off Ratio | Minimum Static Inter-Base Resistance | JEDEC-95 Code | JESD-609 Code | Minimum Valley Point Current | Maximum Time At Peak Reflow Temperature (s) | Peak Reflow Temperature (C) | Maximum Peak Point Current |
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Unijunction Transistors (UJT) are three-terminal semiconductor devices that are used in a variety of applications such as timing, triggering, and oscillation circuits.
A UJT consists of a lightly doped n-type silicon bar with a p-type material implanted in the center, forming two p-n junctions. The two outer ends of the n-type bar are the emitter (E) and collector (C) terminals, while the p-type material in the center is the base (B) terminal. The UJT has a high input impedance and a low output impedance.
When a voltage is applied to the emitter terminal, it causes a small forward bias on the emitter-base junction, which allows a small current to flow into the base region. As the voltage across the UJT increases, the emitter-base junction reaches a point where the current into the base region increases rapidly. This point is known as the "peak-point voltage" or Vp. Once the emitter-base junction is forward biased, the UJT behaves like a negative resistance device, with the current increasing as the voltage decreases.
UJTs are often used in relaxation oscillator circuits and as voltage-controlled switches. In oscillator circuits, the UJT is used to provide a timing signal that can be used to trigger other devices, such as thyristors or triacs. In switching applications, the UJT is used to control the turn-on and turn-off of other devices, such as transistors or SCRs.