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www.newark.com

Page <1>

V1.0

10/09/12

Unijunction Transistor

Description:

   A PN unijunction transistor in a TO-92 type package designed for use in pulse 

and timing circuits, sensing circuits and thyristor trigger circuits

Absolute maximum Ratings :  

(Ta = +25 °C unless otherwise specified)
Power Dissipation, P

d

 

: 300mW

Derate Above 25 °C 

: 3.0mW/ °C

RMS Emitter Current, I

e

(

rms

) 

: 50mA

Peak Pulse Emitter Current (Note 1) Current, i

e

  : 1.5A

Emitter Reverse Voltage, V

b

2

e

 

: 30V

Interbase Voltage, V

b

2

b

1 

: 35V

Operating Junction Temperature Range, T

j

 

: -65 °C to +125 °C

Storage Temperature Range, Tstg 

: -65 °C to +150 °C

Notes:

1. Duty Cycle <=  1% PRR = 10PPS.
2. Based upon power dissipation at Ta = +25 °C
3.  Intrinsic standoff ratio is essentially constant with temperature and interbase voltage and is defined by the 

equation:

 

 

 

Vp - Vbb + Vd

          Where: Vp = Peak Point Emitter Voltage; Vbb = interbase Voltage;  

Vd = Junction Diode Drop (~0.5V).

5.  Use Pulse techniques: Pulse width ~ 300 µS, Duty Cycle  <=  2% to avoid internal heating due to inter-

base modulation which may result in erroneous readings 

Electrical Characteristics: (T

a

 = +25 ºC Unless otherwise specified)

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

Instrinsic Standoff Ratio

V

b

2

b

1

 = 10V, Note3

0.56

-

0.75

-

Interbase Resistance

r

bb

4

6

9.1

k٦

Interbase Resistance Temperature 

Coefficient

0.1

-

0.9

%/ ºC

Emitter Saturation Voltage

V

eb

1(sat)

V

b

2

b

1

 = 10V, I

e

 = 50mA, Note 4

-

2.5

-

V

Modulated interbase Current

I

b

2(mod)

V

b

2

b

1

 = 10V, I

e

 = 50mA

-

15

-

mA

Emitter Reverse Current

I

eb

20

V

b

2

e

 = 30V, I

b

1

 = 0

-

0.005

1

µA

Peak Point Emitter Current

I

p

V

b

2

b

1

 = 25V

-

1

5

µA

Valley Point Current

I

v

V

b

2

b

1

 = 20V, R

b

2

 = 100Ω¦, Note 4

2

5

-

mA

Base-One Peak Pulse Voltage

V

O

b

1

3

6

-

V

www.element14.com
www.farnell.com
www.newark.com

Page <2>

V1.0

10/09/12

Unijunction Transistor

Important Notice : This data sheet and its contents (the †œInformation†�) belong to the members of the Premier Farnell group of companies (the †œGroup†�) or are licensed to it. No licence is granted 

for the use of it other than for information purposes in connection with the products to which it relates. No licence of any intellectual property rights is granted. The Information is subject to change 

without notice and replaces all data sheets previously supplied. The Information supplied is believed to be accurate but the Group assumes no responsibility for its accuracy or completeness, any 

error in or omission from it or for any use made of it. Users of this data sheet should check for themselves the Information and the suitability of the products for their purpose and not make any  

assumptions based on information included or omitted. Liability for loss or damage resulting from any reliance on the Information or use of it (including liability resulting from negligence or where the 

Group was aware of the possibility of such loss or damage arising) is excluded. This will not operate to limit or restrict the Group’s liability for death or personal injury resulting from its negligence. 

Multicomp is the registered trademark of the Group. © Premier Farnell plc 2012.

Part Number Table

Description

Part Number

Unijunction Transistor, TO-92, PN

2N4870

Dim

Min

Max

A

4.3

5.33

B

4.45

5.2

C

3.18

4.19

D

0.41

0.55

E

0.35

0.5

F

5 º

G

1.14

1.4

H

1.14

1.53

K

12.7

-

Dimensions : Millimetres

 

       

         
EN - For pricing and availability in your local country please visit one of the below links: 
 
DE - Informationen zu Preisen und Verfügbarkeit in Ihrem Land erhalten Sie Ã¼ber die unten aufgeführten Links: 
 
FR - Pour connaître les tarifs et la disponibilité dans votre pays, cliquez sur l'un des liens suivants: 
 
 
 
 
 

EN 
This Datasheet is presented by 
the manufacturer 

DE 
Dieses Datenblatt wird vom 
Hersteller bereitgestellt 

FR 
Cette fiche technique est 
présentée par le fabricant