Hi bc547 is an NPN BD137 is a bigger transistor (no),bc557 is a PNP (no), 2n3904 is an equivalent(yes) I do not know 1C128.instead of bc547 for amplfier which transistor i can use out of BD137,BC557,2N3904,1C128
by Aaron Carman
by Jake Hertz
by Jake Hertz
by Jake Hertz