Onsemi Unijunction Transistors (UFT) 18

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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

2N2420B

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.56

9.1 kohm

BOTTOM

O-MBCY-W3

.68

6.2 kohm

TO-18

e0

8 mA

6 mA

2N492C

Onsemi

SINGLE

NO

.45 W

METAL

SWITCHING

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.56

9.1 kohm

BOTTOM

O-MBCY-W3

.68

6.2 kohm

TO-5

e0

8 mA

2 mA

2N2421B

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

TIN LEAD

.62

6.8 kohm

BOTTOM

O-MBCY-W3

Not Qualified

.75

4.7 kohm

TO-18

e0

8 mA

6 mA

2N2422A

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.62

9.1 kohm

BOTTOM

O-MBCY-W3

.75

6.2 kohm

TO-18

e0

8 mA

12 mA

2N2419B

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.56

6.8 kohm

BOTTOM

O-MBCY-W3

.68

4.7 kohm

TO-18

e0

8 mA

6 mA

2N2419A

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.56

6.8 kohm

BOTTOM

O-MBCY-W3

.68

4.7 kohm

TO-18

e0

8 mA

12 mA

2N494C

Onsemi

SINGLE

NO

.45 W

METAL

SWITCHING

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.62

9.1 kohm

BOTTOM

O-MBCY-W3

.75

6.2 kohm

TO-5

e0

8 mA

2 mA

W4893

Onsemi

NO

Unijunction Transistors

.55

12 kohm

.82

4 kohm

2 mA

2 mA

2N2421A

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.62

6.8 kohm

BOTTOM

O-MBCY-W3

.75

4.7 kohm

TO-18

e0

8 mA

12 mA

P2647

Onsemi

NO

Unijunction Transistors

.68

9.1 kohm

.82

4.7 kohm

4 mA

5 mA

2N2417B

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.51

6.8 kohm

BOTTOM

O-MBCY-W3

.62

4.7 kohm

TO-18

e0

8 mA

6 mA

P2646

Onsemi

NO

Unijunction Transistors

.56

9.1 kohm

.75

4.7 kohm

4 mA

5 mA

2N2418A

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.51

9.1 kohm

BOTTOM

O-MBCY-W3

.62

6.2 kohm

TO-18

e0

8 mA

12 mA

2N1671C

Onsemi

SINGLE

NO

.45 W

METAL

SWITCHING

50 mA

WIRE

ROUND

1

35 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.47

9.1 kohm

BOTTOM

O-MBCY-W3

.62

4.7 kohm

TO-5

e0

8 mA

2 mA

2N2417A

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.51

6.8 kohm

BOTTOM

O-MBCY-W3

.62

4.7 kohm

TO-18

e0

8 mA

12 mA

2N490C

Onsemi

SINGLE

NO

.45 W

METAL

SWITCHING

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.51

9.1 kohm

BOTTOM

O-MBCY-W3

.62

6.2 kohm

TO-5

e0

8 mA

2 mA

2N2418B

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.51

9.1 kohm

BOTTOM

O-MBCY-W3

.62

6.2 kohm

TO-18

e0

8 mA

6 mA

2N2420A

Onsemi

SINGLE

NO

.3 W

METAL

70 mA

WIRE

ROUND

1

65 V

3

CYLINDRICAL

Unijunction Transistors

140 Cel

SILICON

-65 Cel

Tin/Lead (Sn/Pb)

.56

9.1 kohm

BOTTOM

O-MBCY-W3

.68

6.2 kohm

TO-18

e0

8 mA

12 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.