Hello, I have a question regarding the gate current sine wave of an SCR
circuit.

I am asked to sketch the output voltage on top of the supply voltage waveform and the required gate current below it when the SCR delay angle is 45°

I have sketched the output voltage sine wave, but the gate current sine wave I am not sure about.
I think there will be a positive rise in gate current until the trigger current is reached and the SCR turns on and then the gate current decreases to near 0.

My output voltage sketch is similar to the sine wave in this image

Where the black line wave is the output voltage and the red line is the
AC source.

I have been trying to find a gate current sine wave image to compare with
it. Can any one describe the gate current wave form or give a link to an image of such?

Any suggestions for programs to draw sine waves?

Attached is a circuit similar to that shown with the question.

 

You might find what you are looking for in this chapter of our Ebook - http://www.allaboutcircuits.com/vol_3/chpt_7/5.html

 

Thanks, I have looked at that chapter and the link for the image
in my post is from that page.

I am guessing now but will the gate current look similar to the portion
missing from the positive output voltage sine wave?