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Transistor help please

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Akshay123

New Member
Hi eveyone, first post on here so please go easy. ;)

Basically I am building a circuit but one of the transistors I have (BC547) did not come with the leg arrangement labelled. I have checked online data sheets but each one has says something different. I have a digital multimeter at home with sockets for transistor legs labelled E, B, C.

Is there an easy way using the meter that I can check to see what leg is what please?
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi eveyone, first post on here so please go easy. ;)

Basically I am building a circuit but one of the transistors I have (BC547) did not come with the leg arrangement labelled. I have checked online data sheets but each one has says something different. I have a digital multimeter at home with sockets for transistor legs labelled E, B, C.

Is there an easy way using the meter that I can check to see what leg is what please?
hi,
Who is the manufacturer of your BC547.?? its a 'logo' on the device.
 

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Akshay123

New Member
Hi I bought it from Maplin but couldn't see a manufacturer logo on it. I would like to make sure using the multimeter because I've been having problems with the circuit and this transistor plays a key role in doing what I want to achieve.
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi I bought it from Maplin but couldn't see a manufacturer logo on it. I would like to make sure using the multimeter because I've been having problems with the circuit and this transistor plays a key role in doing what I want to achieve.
Look at this image from a text book.

Using a multimeter on resistance or 'diode' function you should be able to measure the base to emitter junction [ approx 800R]
 

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Akshay123

New Member
I have little sockets on the multimeter labelled E, B, C so how do I use this feature to find out what leg is what on the transistor? It's been driving me nuts for ages and I can't get my circuit to work without frying each transistor through trial and error! :confused:
 

ericgibbs

Well-Known Member
Most Helpful Member
I have little sockets on the multimeter labelled E, B, C so how do I use this feature to find out what leg is what on the transistor? It's been driving me nuts for ages and I can't get my circuit to work without frying each transistor through trial and error! :confused:
Have you tried using the multimeter as described in my last post.??

Post your circuit so that we can check it out.
 

dougy83

Well-Known Member
I have little sockets on the multimeter labelled E, B, C so how do I use this feature to find out what leg is what on the transistor? It's been driving me nuts for ages and I can't get my circuit to work without frying each transistor through trial and error! :confused:
Stick the transistor in the socket and select the 'transistor test' on the multimeter. If your multimeter is anything like my old one, it will display the hfe (gain). Try different positions until you get the highest gain, and then you'll know what the pinout is.
 

Akshay123

New Member
Stick the transistor in the socket and select the 'transistor test' on the multimeter. If your multimeter is anything like my old one, it will display the hfe (gain). Try different positions until you get the highest gain, and then you'll know what the pinout is.
Hi there, so what you're saying is that after experimenting with different leg positions in the multimeter, the arrangement that produces the highest reading on the screen is the correct one?

This is my multimeter - which setting should the dial be on to test the transistor, assuming its an NPN?

http://www.ingram-tech.com/products/meter.jpg

This is the circuit I am trying to build. The transistor in question (BC547) is TR1.
 

Bob Scott

New Member
Do you see the black outline around the trasistor test socket on your meter, and how the two sides of the line are extended over to the "hFE" switch position? That is the switch position.

Use the socket of the "NPN" side.
 
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Akshay123

New Member
Thanks bud, a picture really does paint a thousand words! I'll try that when I get the chance and report back when done. :)
 
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