This is a circuit that will help you sort the TRANSISTORS you have in your laboratory, and will also help you choose the best of them for your projects. It will also show you if the TRANSISTOR is PNP or NPN.The circuit can also be used to check some types of diodes.The printed circuit board is small and if you use a small box to put it in you will have a convenient and portable TRANSISTOR tester. SUITABLE BOX 2036. V 9VDC PCB 35x43mm