Gate Terminal In SCR

Replies

• 

  [Prototype]

  ​

  
  See the layer diagram of SCR I've made above.
  
  An SCR is nothing but a P-N junction diode & an NPN transistor combined together. There's no significance of gate being near to the cathode side, its just the normal base terminal of an NPN transistor which is being used as GATE in SCR. Since the PN junction doesn't have a 3rd terminal & NPN transistor is used, the GATE automatically happens to be near the cathode.
• 

  arunchary

  its because we know the simple concept of current,cathode have a more no.of electrons to drive then anode.little bit of gate current which leads to drive and then it will starts conducting.....
• 

  Jeffrey Arulraj

  Sorry to say this guys both have hinted on a wrong tone
  
  The prime reason is to provide an addtional voltage to the reverse biased PN junction (2nd junction) and thus we get a breakdown before the actual reverse bias break down voltage (say 30 V this is supplied partly from AK voltage and partly from the Gate voltage so earlier BD for lesser AK voltage )
  
  If the Gate is connected nearer to the Anode more voltage will be needed to trigger the SCR as higher voltage will be required to breakdown the reverse biased diode in junction 2
• 

  Vishal Sharma

  Just now learned the topic in college. I totally agree with jeffrey
• 

  [Prototype]

  jeffrey samuel

  Sorry to say this guys both have hinted on a wrong tone
  
  The prime reason is to provide an addtional voltage to the reverse biased PN junction (2nd junction) and thus we get a breakdown before the actual reverse bias break down voltage (say 30 V this is supplied partly from AK voltage and partly from the Gate voltage so earlier BD for lesser AK voltage )
  
  If the Gate is connected nearer to the Anode more voltage will be needed to trigger the SCR as higher voltage will be required to breakdown the reverse biased diode in junction 2

  I always thought there was no functional significance of that. Thanks for enlighting. Guess my attention was somewhere else when this thing was taught.
• 

  Vishal1485

  practically this terminals are arranged in sequence cathode, anode & gate
• 

  Jeffrey Arulraj

  Vishal1485

  practically this terminals are arranged in sequence cathode, anode & gate

  That is only in a chip or in the pin diagram of the SCR which you use in lab not in the internal structure friend