IDENTIFY Transistor from its Hfe Value

[BHARGAV SHANKHALPARA]

Hello all..!!

i am working on one project. in that i want to use transistors as switching mechanism. actually i am building this circuit based on one old circuit.

in old circuit i find two transistor in T0-220 package.Transistor name are not seen.

i have PEAK SEMICONDUCTOR COMPONENT ANALYZER, it can also detect leads of transistor automatic.



i connect my old circuit transistor to it one by one. and i got following data for each transistor

TRANSISTOR ONE DATA :

1 ) Device Type : NPN SILICON TRANSISTOR
2) Test Current Ic = 2.50mA
3) Base Emitter Voltage Vbe =0.67V
4) Test Current Ib = 4.62mA
5) Leakage Current Ic = 0.00mA.
6) Hfe = 76

TRANSISTOR TWO DATA:

1 ) Device Type : NPN SILICON TRANSISTOR
2) Test Current Ic = 2.50mA
3) Base Emitter Voltage Vbe =0.67V
4) Test Current Ib = 4.62mA
5) Leakage Current Ic = 0.00mA.
6) Hfe = 78

My problem is that...after getting this data i have i search many datasheet of transistor, there is no any matching of this Hfe.

How i can find perfect transistor..?

is above parameters are enough..?

please suggest what to do..?

 

[davenn]

My problem is that...after getting this data i have i search many datasheet of transistor, there is no any matching of this Hfe.

you wont, there could be dozens or 100's of transistors with similar values

How i can find perfect transistor..?

doesn't exist !!

is above parameters are enough..?

enough for what ?

please suggest what to do..?

if either of those transistors that you tested above have ratings that will suit your circuit
then use it .... who care what type number it is


Dave

 

[BHARGAV SHANKHALPARA]

Hello dave...

I want to obtain same function as my old circuit does but part number is not readable. these transistor working perfectly so this switching section i copied from that.

I want part number because i want to buy this part, one the base of Hfe suppliers not supplies part. I think.

 

[shrtrnd]

Do you hve access to a 'Curve Tracer',
You can narrow your search with more specific parameters.
davenn explained that there will be many transitors with close similarities to what you're asking for.
A good plot of your transistor's characteristic curve should help you find the closest matches if you compare data sheets.

 

[BHARGAV SHANKHALPARA]

Hello..shrtrnd..

Sorry but i haven't Curve Tracer..!!

 

[BobK]

The main characteristics you are interested in for picking a transistor in a switching application are:

Vceo - the breakdown voltage between emitter and collector
Ic - the max collector current
Hfe - the common emitter current gain
Vcesat - the saturation voltage between emitter and collector

Determine what you need for each of these parameters and then pick a transistor that meets or exceeds them.

Bob

 

[duke37]

Speed may also be important. Switching at a few kHz should be no problem. Switching at 1MHz may be.

Also, power dissipation.

Can you describe what the circuit does and if possible show a diagram?

 

[BHARGAV SHANKHALPARA]

In my application slow switching speed in few Hz.

 

[Colin Mitchell]

Use any transistor. The gain of the transistor is not important in you case if the current is small.

 

[BHARGAV SHANKHALPARA]

Finally after doing some try and error i found TIP31 and TIP122 works fine.

Thank you to all for your suggestions...!!

 

[Colin Mitchell]

Just as I said. One has a gain of 50 and the other 1,000 an yet they both work ok.
The gain is rarely important.