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Transistor Characteristic curves

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Nethra

New Member
I am trying to get the VI curves of the BC 107 NPN transistor, in common emitter configuration.
I face two issues:
1) Input characteristics :The base current is linearly increasing with the base emitter voltage , which is not the actual case seen in the model graph.(Vce was fixed)
2) Output characteristics: There is no flow of collector current even with increase in the collector emitter voltage.( Base current was fixed to a particular value)
I need some help to rectify the errors. Please do suggest an alternative method if any.
 

ronsimpson

Well-Known Member
Most Helpful Member
Please show your circuit.
How are you getting your results. (SPICE or bread board)
Do you have a emitter resistor to ground.
Base current=? Emitter current=? Collector current=?
 

spec

Well-Known Member
Most Helpful Member
I am trying to get the VI curves of the BC 107 NPN transistor, in common emitter configuration.
I face two issues:
1) Input characteristics :The base current is linearly increasing with the base emitter voltage , which is not the actual case seen in the model graph.(Vce was fixed)
2) Output characteristics: There is no flow of collector current even with increase in the collector emitter voltage.( Base current was fixed to a particular value)
I need some help to rectify the errors. Please do suggest an alternative method if any.
Hi Nethra,

As you imply there is something wrong with your test jig. Would you like to post a schematic showing the circuit of you test jig.

Or would you jut like one of us to post a suitable circuit?

spec
(same thoughts again Ron:joyful:)
 

spec

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Most Helpful Member
POST ISSUE 2 of 2017_02_01

Hi again Nethra,

below is a sketch showing a suitable small signal NPN BJT DC test jig. Just reverse the power lines to test a PNP BJT.

A nice touch would be to make RV1 a ten-turn potentiometer.

spec

2017_02_01_ETO_Iss2_TRANSISTOR_TESTER_V1.jpg
 
Last edited:

audioguru

Well-Known Member
Most Helpful Member
Hi Spec,
Isn't your transistor testy jig designed for a power transistor on a heatsink?
With a 12V supply the poor little transistor will saturate with a collector current approaching 1.2A! If the trimpot is turned down so the transistor is linear then it will melt when it dissipates 3.6W!
 

ronsimpson

Well-Known Member
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hi Spec,

We don't know much!
The base current is linearly increasing with the base emitter voltage
I think the voltage is measured from (A) to ground and not B-E. This error will make the current be linear as described.
no flow of collector current
Maybe the E and C are wrong. Common mistake. Maybe the transistor is damaged. Common.

 

spec

Well-Known Member
Most Helpful Member
Hi Spec,
Isn't your transistor testy jig designed for a power transistor on a heatsink?
With a 12V supply the poor little transistor will saturate with a collector current approaching 1.2A! If the trimpot is turned down so the transistor is linear then it will melt when it dissipates 3.6W!
Thanks AG,

That's what happens when I do not pay attention.:banghead:

spec

(schematic of post #4 now updated)
 

spec

Well-Known Member
Most Helpful Member
hi Spec,

We don't know much!

I think the voltage is measured from (A) to ground and not B-E. This error will make the current be linear as described.

Maybe the E and C are wrong. Common mistake. Maybe the transistor is damaged. Common.

Hi Ron,

Yea, looks like something like that. It may seem odd to us that there could be a problem measuring the parameters of a BJT but, as you can see from AG's post #5, I made a cock of it, and looking back to my first adventures with transistors (OC71, OC44) I had a few disasters.:eek:

spec
 

Nethra

New Member
Thank you all.. but then I am sure that the transistor is working fine and the emitter and collector are placed correctly.

I am using a bread board circuit. The emitter is grounded directly.

Please show your circuit.
How are you getting your results. (SPICE or bread board)
Do you have a emitter resistor to ground.
Base current=? Emitter current=? Collector current=?
 

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audioguru

Well-Known Member
Most Helpful Member
I think you burned out the poor little 50 years old transistor and now its base-emitter is just a piece of carbon resistance.
The datasheet for the old BC107 says its maximum allowed continuous collector current is only 100mA but with your 100 ohm collector resistor then with a 30V supply the maximum current is 295mA.
The datasheet has a graph showing that with a collector current of 10μA the typical base-emitter voltage is 510mV, with 100μA the voltage is 545mV, with 1mA the voltage is 0.6V, with 10mA the voltage is 675mA and with 100mA the voltage is 760mA which are non-linear like a silicon diode.
Of course the base-emitter voltage drops as the transistor heats up.
 
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