The Spike in Question :(

[Lord Loh.]

Here is a circuit that is a part of my project. The problem is the two spikes that I just cannot explain.

I am as much intrested in knowing why they are there as much as getting rid of them.

Please Help.

Thank you.

 

[E-design]

My guess would be the large miller and output capacitances present with the 2N3055 power transistors. As soon as you turn on the one device, the falling transition on the collector is coupled through the C-B capacitance of the other device, causing the negative spike on that base. Try using small signal transistors with much lower internal capacitances.