2N4870 - NTE ELECTRONICS, INC.

2N4870

Unijunction Transistor (UJT)

TO−92 Type Package

Description:

The 2N4870 is 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 other specified)

RMS Power Dissipation, PD300mW.....................................................

Derate Above 25C 3.0mW/C.....................................................

RMS Emitter Current, IE50mA...........................................................

Peak−Pulse Emitter Current (Note 1), IE1.5A..............................................

Emitter Reverse Voltage, VB2E 30V.......................................................

Interbase Voltage (Note 2), VB2B1 35V....................................................

Operating Junction Temperature Range, TJ −65 to +125C.................................

Storage Temperature Range, Tstg −65 to +150C..........................................

Note 1. Duty cycle  1%, PRR = 10 PPS

Note 2. Based upon power dissipation at TA = +25C

Electrical Characteristics: (TA = +25C unless other specified)

Parameter Symbol Test Conditions Min Typ Max Unit

Intrinsic Standoff Ratio VB2B1 = 10V, Note 3 0.56 −0.76

Interbase Resistance RBB 4.0 6.0 9.1 k

Interbase Resistance Temperature Coefficient RBB VB2B1 = 3V, IE = 0,

TA = −65 to +125C

0.1 −0.9 %/C

Emitter Saturation Voltage VBE1(sat) VB2B1 = 10V, IE = 50mA, Note 4 −2.5 −V

Modulated Interbase Current IB2(Mod) VB2B1 = 10V, IE = 50mA −15 −mA

Emitter Reverse Current IEB2O VB2E = 30V, IB1 = 0 −0.005 1.0 A

Peak−Point Emitter Current IPVB2B1 = 25V −1.0 5.0 A

Valley−Point Current IVVB2B1 = 20V, RB2 = 100, Note 4 2.0 5.0 −mA

Base−One Peak Pulse Voltage VOB1 3.0 6.0 −V

Note 3. Intrinsic standoff ratio, is defined in terms of peak−point voltage, VP

, by means of the equa-

tion: VP =  VB2B1 + VF

, where VF is approximately 0.49 volts at +25C @ IF = 10A and

decreases with temperature at approximately 2.5mV/C. Components R1, C1, and the UJT

form a relaxation oscillator, the remaining circuitry serves as a peak−voltage detector. The

forward drop of Diode D1 compensates for VF

. To use, the “call” button is pushed, and R3

is adjusted to make the current meter, M1, read full scale. When the “call” button is released,

the value of  is read directly from the meter, if full scale on the meter reads 1.0.

Note 4. Use pulse techniques: PW  300s, duty cycle  2.0% to avoid internal heating, which may

result in erroneous readings.