What is Programmable Unijunction Transistor?

[bittware]

programmable unijunction transistor

Hello experts,
What is Programmable Unijunction Transistor? What is its characteristics?
How to use it in implementing a timer?
Any typical application explaination will be much helpful.

Thanks in advance!

 

[samcheetah]

programmable unijunction transistor application

as the name suggest it is something programmable and it is a transistor which has one junction. basically it has one P and one N layer. two electrodes, cathode and anode are embedded in the N layer. the P layer is embedded in the N layer and a Gate terminal is connected to the P layer. so basically you have a PN junction but it acts quite different from the PN junction diode.

now its called programmable because of a great ability it has. its not like a program has to be written in assembly and burnt onto the PUT but its the gate voltage that programs the behaviour of the PUT. like in a diode a voltage between the anode and the cathode has to be greater than the knee voltage. same is the case here but with a PUT the voltage between the anode and the cathode has to be greater than the gate voltage. so thats what programs the behaviour of the PUT.

an application example would be a sawtooth generator. its basically a ramp generator but each time the voltage between the anode and the cathode of a PUT exceeds the gate voltage the PUT starts conducting and the waveform obtained resembles a sawtooth.

google for more info

 

[ikru26]

put (programmable unijunction transistor)

he Programmable Unijunction Transistor behaves much like a unijunction transistor (UJT), but is "programmable" via external resistors (that is, you can use two resistors to set a PUT's peak voltage). Note that the name is a bit of a misnomer -- as a thyristor, it is a four layer device, unlike a true unijunction transistor which has but two layers.

Like other thyristors, a PUT looks much like a junction transistor with a fourth layer and therefore a total of three P-N junctions. Meanwhile, a third terminal, the gate (G), makes a PUT function like a hybrid of transistor and diode:
PUT symbolPUT cross-section

PUTs are not often used in BEAM; they're essentially special-purpose devices in electronics, used for lighting control, motor speed control and other variable power applications. In combination with an SCR they can, though, make a mean solar engine.

In a pinch, you can build up something much like a PUT from discrete transistors wired as a complementary feedback pair:
Image

Here, as soon as any current flows in either transistor, this current becomes base current for the other transistor, and both transistors turn on hard. This means you can only build up this circuit using low-leakage transistors ('though this should be the case with any decent-quality modern transistor ).

 

[sabari]

programmable unijunction transistor how-to

as the name suggest it is something programmable uni junction transistor. basically it has one P and one N layer. two electrodes, cathode and anode are embedded in the N layer. the P layer is embedded in the N layer and a Gate terminal is connected to the P layer. so basically you have a PN junction but it acts quite different from the PN junction diode.
now its called programmable because of a great ability it has. its not like a program has to be written in assembly and burnt onto the PUT but its the gate voltage that programs the behaviour of the PUT. like in a diode a voltage between the anode and the cathode has to be greater than the knee voltage. same is the case here but with a PUT the voltage between the anode and the cathode has to be greater than the gate voltage. so thats what programs the behaviour of the PUT. it is used to generate sawtooth waveform which r used for triggering circuits.

 

[engr.fawad]

a complete article about Programable UJT here

PUT - Programmable Uni-junction Transistor

PUT - Programmable Unijunction Transistor | daenotes.com