Circuits with semiconductor devices

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PG1995

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Hi

Could you please help me with this query about Shockley diode? Thank you.

Regards
PG

PS: For etymology of the words "thyristor" and "thyratron", please have a look on **broken link removed**.
 

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hi PG,
The current flowing thru the resistor and diode [ when the cap has discharged] is less than the required HOLDING current of the diode, so it turns off.
Look at this pdf.
E
 

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Thank you, Eric.

The following definition from the PDF is very helpful.


Regards
PG
 
Hi

Could you please help me with these queries about a UJT (unijunction transistor)? Thank you.

Regards
PG
 

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PG1995 said:
Hi

Could you please help me with these queries about a UJT (unijunction transistor)? Thank you.

Regards
PG
Click to expand...

I can't event read that .jpg

Never mind, it's my new viewer, I have to click on the Web version.

Edit: Thanks for the post, I never even new there was a UJT. Until now.
 
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hi PG,
This pdf explains the valley voltage characteristic of a UJT
Dont forget the UJT is formed using a 'semiconductor' material, so it will have an intrinsic resistance from B1 to B2, usually around 10K
E
 

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Thanks, Eric.

Dont forget the UJT is formed using a 'semiconductor' material, so it will have an intrinsic resistance from B1 to B2, usually around 10K
Click to expand...

I understand this but it's an n-type material which means it has some free electrons which means a bad conductor, and a bad conductor isn't really such a good insulator that it can offer resistance of 10 kΩ. I know I'm missing something here. So, I still need a little more help with Q1 here, and if possible, please do let me know if my interpretation in Q2 is okay.

Regards
PG
 

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Q1
Wire 5 and wire 6 have a physical presence so there will be capacitance between them.
If the electrical connections to the right hand side of wires 5 and 6 have exactly the same characteristics, then the voltage across C_n will be zero, and that capacitance will have no effect on operation.
If wires 5 and 6 have different electrical loads at their right hand sides, then as the voltage from wire 2 varies, then the voltages on wires 5 and 6 will be different, and so C_n becomes significant.

Q2
The double capacitor with the centre tap connected to ground is just an easy way of drawing two separate capacitors,
(one capacitor from wire 5 to ground, the other from wire 6 to ground), in a limited space on the screen/paper.

JimB
 
Hi,

Just a quick note here...

I see a lot of questions about the unijunction transistor. These transistors are rarely used these days. I have only encountered one real circuit that had one in it in the last 40 years. There may still be schematics around though and there's a chance someone somewhere might use one, but i think it will be very rare.
 
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