Regarding SCR gate voltage

[chintan_gaurav8]

Hi,

I have implemented the ckt as attached in 1.jpg file. As shown in ckt, the d.c supply which gives the voltage to gate terminal is kept at 0 v. But when i am connecting the supply terminal to gate terminal its gate voltage is increase from 0 volt to 3.6 volt ( 5 volt(voltage devider) - IR(1kohm) ). So now if i am increase the gate voltage to fire SCR, voltage across anode to cathod will not decrease abruptly as per the characteristic of SCR but it will decrease slowly as we increase the gate voltage and reach to 0.7 volt when gate voltage is around 10.7 volt. Can i say SCR is fired?

Now i have implement the ckt as attached in 2.jpg file. At that time when i am connecting the supply terminal to gate terminal its gate voltage remains at 0 volt and when increase gate voltage voltage across anode to cathod will decrease abruptly as per the SCR characteristic.
Can any one tell me what is the reason?

View attachment 41050

View attachment 41051

 

[ARUN CHOWDARY]

scra are constructed with the semiconductor material silicon as it has large for bidden gap we can only rurn on it by  increasing the voltage than the forward break over voltage  as the gate current increases the forward current decreases :