Transistor Data sheet VBE, IC, and Hfe

Thread Starter

Uponamountain

Joined May 29, 2012
1
HI,

I would like to know how my fancy transistor circuit works over temperature.

Most transistor data sheets provide three temperature ranges for Vbe, Ic, and Hfe.
How does one interpolate these paramters at different temperatures?

For Hfe would one just do a linear interpolation?
Hfe is impacted by temperature and Ic.
Is there a relationship that can be used?

For Vbe would one do a linear interpolation to find the new vbe at some temperature keeping Ic at a constant current then find what the new Vbe would be at a different Ic based on the new Vbe from from the new temperature?
Vbe is impacted by temperature and Ic.
Ic=is*e^(Vbe/vt)

Im just trying to understand how I can use the data sheet to get other values Hfe, Vbe, and Ic at different temperatures so I can model my circuits more accurately.

If you have any good reading to point me to that would be most welcome.
or maybe I am making this more complicated than need be???

Thank you
 

cabraham

Joined Oct 29, 2011
82
The data sheets give this info. You can find graphs of hFE vs. temp, VBE vs. temp, & hFE vs. IC over varying temp. Also given is VBE vs. IC over varying temp. It's all there. Just examine the data sheet, & you should be able to obtain whatever you need.

I've attached 2 data sheets, 1 for the 2222 npn device, & 1 for its counterpart, the 2907 pnp device. If you wish I can answer any questions, but first please look them over carefully. You will find what you need on the data sheets. BR.

Claude
 

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Audioguru

Joined Dec 20, 2007
11,251
Transistors have a wide range of hFE and Vbe in addition to changes in them with temperature change. If you design a circuit for only one value of hFE and/or Vbe then it probably will not work properly with many transistors and many temperatures even if the transistors have the same part number.

So we design a circuit of a common-emitter amplifier with a voltage divider biasing the base and an emitter resistor adding a fixed voltage to Vbe and negative feedback so that changes in the hFE, Vbe, temperature and supply voltage do not make much difference.
 

ScottWang

Joined Aug 23, 2012
6,779
Show your value of Ib, Ic, Ie and Hfe, and the circuit and the value of resistors, it's more easier to analyze and to know what happened?
 
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