It depends on what you have your transistors do. You could even have one single transistor that you switch on/off very very quickly. You'd need to find a transi

It depends on what you have your transistors do. You could even have one single transistor that you switch on/off very very quickly. You'd need to find a transistor with sub-ns switching time to reach >1GHz. It's not a very interesting "computation," though.