I have finish a project with avr ,electronic ignition with adjustable advance, for one cylinder engine.
The ignition coil from this engines is connected to ground and ignition module switching the positive.
I have make my test with standard bipolar transistor and work but not as we like to work ,we don't have enough current to coil ,comparing with oem ignition module.
I am thinking to use p channel mosfet transistor, because mosfet have low resistance from source to drain, in parallel but i don't know what type to use there are a million types out there.
Avr give high output for every pulse so I use first npn transistor to drive power pnp transitor or p channel mosfet