For example, it depends on in which type of circuit you are replacing it. There are different situations in which sometimes you can use the 2N3904 instead of 2N2222 and sometimes not. As you can see the 2N3904 collector current is 200mA while the 2N2222 collector current is 600mA. But when we look at the collector current there is much difference between the two. The total device dissipation of both the transistors is also the same which is 625mW and the (fT) or transition frequency is also the same which is 300MHZ.

Looking at the above ratings and characteristics comparison table we can see that the collector to emitter voltage of both transistors is same. Ratings & Characteristics Comparison : Ratings & Characteristicsīefore using 2N3904 in place of 2N2222 there are some important factors you should consider.

Looking at the pinout of the transistor both transistor have same pin configuration such as the first pin is Emitter, second is Base and the third is Collector. As you can see in the above image that both the transistor looks almost identical from the outside because both have same TO-92 package.

Download 2n2222 pinout