Texas Instruments Unijunction Transistors (UFT) 38

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Part	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	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	Minimum Valley Point Current	Maximum Time At Peak Reflow Temperature (s)	Peak Reflow Temperature (C)	Maximum Peak Point Current
2N2646	Texas Instruments	SINGLE	NO	.3 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	125 Cel	SILICON	-65 Cel	.56	9.1 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.75	4.7 kohm	TO-18	4 mA	NOT SPECIFIED	NOT SPECIFIED	5 mA
2N4948	Texas Instruments	SINGLE	NO	.36 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	200 Cel	SILICON	-65 Cel	.55	12 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.82	4 kohm	TO-18	2 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N4852	Texas Instruments	SINGLE	NO	.3 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	125 Cel	SILICON	-65 Cel	.7	9.1 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.85	4.7 kohm	TO-18	4 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N489	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.51	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N490	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.51	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N4851	Texas Instruments	SINGLE	NO	.3 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	200 Cel	SILICON	-65 Cel	.56	9.1 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.75	4.7 kohm	TO-18	2 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N491	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.56	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.68	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N1671B	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.47	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	6 mA
2N489A	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.51	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N492	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.56	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.68	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N490B	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.51	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	6 mA
2N4894	Texas Instruments	SINGLE	NO	.3 W	PLASTIC/EPOXY	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	150 Cel	SILICON	-55 Cel	.74	12 kohm	BOTTOM	O-PBCY-W3		Not Qualified	.86	4 kohm		2 mA	NOT SPECIFIED	NOT SPECIFIED	1 mA
2N493B	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.62	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.75	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	6 mA
2N4853	Texas Instruments	SINGLE	NO	.3 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	125 Cel	SILICON	-65 Cel	.7	9.1 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.85	4.7 kohm	TO-18	6 mA	NOT SPECIFIED	NOT SPECIFIED	.4 mA
2N494	Texas Instruments	SINGLE	NO	.45 W	METAL		70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.62	9.1 kohm	BOTTOM	O-MBCY-W3		Not Qualified	.75	6.2 kohm	TO-5	12 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N494A	Texas Instruments	SINGLE	NO	.45 W	METAL		70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.62	9.1 kohm	BOTTOM	O-MBCY-W3		Not Qualified	.75	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	15 mA
2N4893	Texas Instruments	SINGLE	NO	.3 W	PLASTIC/EPOXY	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	150 Cel	SILICON	-55 Cel	.55	12 kohm	BOTTOM	O-PBCY-W3		Not Qualified	.82	4 kohm		2 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N4949	Texas Instruments	SINGLE	NO	.36 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	200 Cel	SILICON	-65 Cel	.74	12 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.86	4 kohm	TO-18	2 mA	NOT SPECIFIED	NOT SPECIFIED	1 mA
2N1671	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.47	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	25 mA
2N494B	Texas Instruments		NO	.45 W			70 mA				65 V			Unijunction Transistors	140 Cel		-65 Cel	.62	9.1 kohm					.75	6.2 kohm		8 mA			6 mA
JAN2N4948	Texas Instruments																						Not Qualified
2N492A	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.56	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.68	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N489B	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.51	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	6 mA
2N4892	Texas Instruments	SINGLE	NO	.3 W	PLASTIC/EPOXY	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	150 Cel	SILICON	-55 Cel	.51	9.1 kohm	BOTTOM	O-PBCY-W3		Not Qualified	.69	4 kohm		4 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
TIS43	Texas Instruments	SINGLE	NO	.36 W	PLASTIC/EPOXY	SWITCHING		WIRE	ROUND	1		3	CYLINDRICAL	Unijunction Transistors		SILICON			9.1 kohm	BOTTOM	O-PBCY-W3		Not Qualified	.82		TO-92	2 mA	NOT SPECIFIED	NOT SPECIFIED	5 mA
2N1671A	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.47	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	25 mA
2N2160	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	150 Cel	SILICON	-65 Cel	.47	12 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.8	4 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	25 mA
2N492B	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.56	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.68	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	6 mA
2N491B	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.56	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.68	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	6 mA
JAN2N491A	Texas Instruments	SINGLE	NO		METAL			WIRE	ROUND	1		3	CYLINDRICAL			SILICON				BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified				8 mA			12 mA
2N3980	Texas Instruments	SINGLE	NO	.36 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	200 Cel	SILICON	-65 Cel	.68	8 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.82	4 kohm	TO-18	1 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N491A	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.56	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.68	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N4947	Texas Instruments	SINGLE	NO	.36 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	200 Cel	SILICON	-65 Cel	.51	9.1 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.69	4 kohm	TO-18	4 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA
2N4891	Texas Instruments	SINGLE	NO	.3 W	PLASTIC/EPOXY	SWITCHING	50 mA	WIRE	ROUND	1	25 V	3	CYLINDRICAL	Unijunction Transistors	150 Cel	SILICON	-55 Cel	.55	9.1 kohm	BOTTOM	O-PBCY-W3		Not Qualified	.82	4 kohm		2 mA	NOT SPECIFIED	NOT SPECIFIED	5 mA
2N493	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.62	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.75	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N493A	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.62	6.8 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.75	4.7 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N490A	Texas Instruments	SINGLE	NO	.45 W	METAL	SWITCHING	70 mA	WIRE	ROUND	1	65 V	3	CYLINDRICAL	Unijunction Transistors	140 Cel	SILICON	-65 Cel	.51	9.1 kohm	BOTTOM	O-MBCY-W3	ISOLATED	Not Qualified	.62	6.2 kohm	TO-5	8 mA	NOT SPECIFIED	NOT SPECIFIED	12 mA
2N2647	Texas Instruments	SINGLE	NO	.3 W	METAL	SWITCHING	50 mA	WIRE	ROUND	1	35 V	3	CYLINDRICAL	Unijunction Transistors	125 Cel	SILICON	-65 Cel	.68	9.1 kohm	BOTTOM	O-MBCY-W3	BASE2	Not Qualified	.82	4.7 kohm	TO-18	8 mA	NOT SPECIFIED	NOT SPECIFIED	2 mA

Unijunction Transistors (UFT)

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.