Unijunction Transistor
| The unijunction transistor(UJT) is a three
terminal device with characteristics very different from the conventional 2 junction,
bipolar transistor. It is a pulse generator with the trigger or control signal applied at
the emitter . This trigger voltage is a fraction (n) of interbase voltage, Vbb.The UJT
circuit symbol, junction schematic, and characteristic curve are shown below. 
The emitter terminal does not inject current into the base
region until its voltage reaches Vp. Once Vp is reached the base circuit conducts and a
postive pulse appears at the B1 terminal and a negative pulse at B2. The UJT incorporates
a negative resistance region, a low emitter current, and a high output pulse current at
terminals B1 and B2, making it an ideal pulse trigger. A simple RC timer circuit using a
UJT is shown below.
The very basic specifications of a UJT are:
(a) Vbb(max) - The maximum interbase voltage that can be
applied to the UJT
(b) Rbb-the interbase resistance of the UJT
(c) n - The intrinsic standoff ratio which defines Vp.
(d) Ip - The peakpoint emitter current
Here are a few of our most
requested UJT's:
| PART
NO. |
RBBO Interbase Resistance @VBB=3V
IE=0(KOhms) |
h
Intrinsic Standoff Ratio @VBB=10V |
Iv
Valley Current Min. (mA) |
Ip
Peak Point Emitter
Current Max. (ľA) |
VOB1
Base One Peak Pulse Voltage Min. (V) |
Package Style |
| 2N489 |
4.7 - 6.8 |
.51 - .62 |
8 |
12 |
-- |
T0-5 |
| 2N490 |
6.2 - 9.1 |
.51 - .62 |
8 |
12 |
-- |
| 2N491 |
4.7 - 6.8 |
.56 - .68 |
8 |
12 |
-- |
| 2N1671 |
4.7 - 9.1 |
.47 - .62 |
8 |
25 |
-- |
| 2N2160 |
4.0 - 12.0 |
.47 - .80 |
8 |
25 |
3 |
| 2N2646 |
4.7 - 9.1 |
.56 - .75 |
4 |
5 |
3 |
TO-18 |
| 2N2647 |
4.7 - 9.1 |
.68 - .82 |
8 |
2 |
6 |
Programmable Unijunction
Transistors (PUT) supplied by American Microsemiconductor
| PART
NO |
Gate to Anode Reverse Voltage Max. (V) |
DC Anode Current Max. (mA) |
IGAO
Leakage
Current @40V Max.
(nA) |
IV
Valley Current
Min. @RG =10k (ľA) |
Vo
Output Voltage
Min. (V) |
| 2N6027 |
40 |
150 |
10 |
70 |
6 |
| 2N6028 |
40 |
150 |
10 |
25 |
6 |
|
American
Microsemiconductor produces a very broad line of standard unijunction transistors.
Many of the basic applications include:
oscillators, timers, sawtooth generators,
SCR triggers, frequency dividers, stable voltage sensing,
P. O. Box 104,
133 Kings Road, Madison, New Jersey 07940, Phone: (973) 377-9566, Fax: (973) 377-3078
Questions, Comments, Suggestions - Email To: info@americanmicrosemi.com |
