How to test a transistor using a digital Multimeter

hi in this video I'm going to show you how to test a transistor using a digital multimeter so before we do that I'm going to show you how to test a diode so this is a typical construction of a diod which basically consists of a two layers of semiconductor been sandwiched together which is a uh which is a p type and N type so when we apply a positive voltage here and negative voltage here a current will start flowing that's we call a forward bias and if we connect the a around positive here and a negative voltage here it uh the current will not flow this is called reverse bias so in forward bias which uh we will using during testing when it's in for bias let's say we Supply at 3 volts when current starts flowing there will be a DI drop or voltage drop or or another other thing it's called a forward voltage forward bias voltage and to measure that is actually quite easy so you just take your multimeter and place the Probe on the diode pin and then you will get the reading for the voltage drop across a DI in this case like Silicon di you will get pretty much close to 0.7 volt now let's move to the transistors so transistors basically consist of three layers of semiconductors that are sandwiched together and it looks like a diode being placed back to back so we can do the same thing the way we test diode so to identify which one's PNP or npn we simply place a probe uh we need to test which uh which pin that and actually conducting so let's for example like we place a positive prob here and a negative probe here or ground probe and then once we place it there we will get a reading which means the current is flowing and also when you when when using a digital multimeter make sure it's in diet setting so it on the probe there's actually a voltage being supplied as well so when you place your probe on the positive or P type and N type which mean it's now in forward bias and you will get the voltage drop on the meter based on across it which is the voltage drop across the PN Junction here so and when okay to find another pin like this one if we place another probe here we also get a a voltage reading on the digital multimeter which means we know that this two pins are P type and the center one is end type then we we also know that this black proof here which is uh doesn't move only this Pro is moving we know that this pin is base base pin and the same thing we do as the npn we simply prove in which one is we have a current flow if we have a current flow let's say we put in this way so we know there's a voltage reading then we know this one is p type this pin is end type so when we move the other way around we also get reading which mean this one is npn since only NE to Pro this moving and the the only one pin is stays uh POS on positive Pro which mean is a p type so we know that it's npn so how do we know which one is B emitter and collectors is actually quite easy and when we measure it let's say this pin right here we will get a voltage forward voltage reading or I mean a voltage drop voltage drop actually it's a voltage drop reading about 0.666 and on this pin we will get somewhere 0.66 9 uh the value is actually not really large but there's significant changes in there so now we know that the the highest uh the highest uh voltage drop across it is uh will it will be called the is called the emitter and this one is the collector pin and this one of course the base pin the reason that this PN Junction on the base emitter uh because the p type on the emitter is heavily dope with impurities that's why it has greater voltage drop compared to a collect the base collector base Junctions okay so that's how you identify which bit which pin is emitter and collector same thing as the npn type so let's try measure one Let's test so I'm going to use normal transistors here I'm going to tell which part it is probably see the label there so so set your multimeter to a diode setting and then I should place it right here there you go so so we have three pins let me show me a bit be too too close Okay so that's test one so when I apply center pin and with the ground Pro and positive Pro now we got a four four bias voltage and when I move this probe around nothing happened so which means that's not the right pin so we move this proe around also get a reading so we know we only move one pro here so which mean this probe is p type uh sorry n type so this one is p type because it's imp positive probe so this p and p so how do we know which one base collect Teter well this proe here the ground probe is basically the base and if we take a look at the multier this one this pin is 708 and this pin is 712 so we know that this one is the emited pin this one is the collector pin and that's how you identify a transistor pins so let's try other transistors I'll put this one on the Bri board hang on I have another transistor here so let's try probing it so let's try the same way do we get the same reading nope this one nope so let's try the other way around there you go we got for bias voltage now let's Pro let's move this Pro around on this side also get a reading so now we know that this pin is p type and this one is n type on this side so we know that it is an npn transistor since there negative Pro here so which one is basic collect met this one is the base because it's the only Pro it doesn't move so this one is 661 this one is six oh sorry this one is in 660 66 1 66 0 so we know that this one is the emitter pin this one is the collector pin because the forward voltage drop across this pin is higher than this one and that's how you identify transistors and which pin is based collector animator and that's all for today and don't forget to subscribe for more future videos

Channel: Shawal SI

Views: 321,717

Keywords: yt:quality=high

Id: Fq9Amy2iAIg

Length: 8min 47sec (527 seconds)

Published: Tue Jul 26 2016