Hello,

I am new to using 555 timer circuits, and stumbled upon this circuit used to generate fast load transients, using a resistive load.

I noticed that for the first 555 timer, pin 7 does not appear connected on the schematic. I tried to run a SPICE simulation, and the circuit does not appear to be working.

Where should pin 7 be connected? Thanks!

Circuit:

http://electronicdesign.com/article/power/fast-load-transient-tester-circuit-features-adjust.aspx

 

After R1. It is the astable multivibrator configuration.