How to convert hFE to Beta for bipolar transistors?

[zlatkoMM]

Hello all...
Why i'm ask this question.So,becose my digital universal mutimeter can only
count transistor hFE.
Well i use Pintar Virtual Lab for my simulatios and he use ß-beta for amplification
factor.
I ask you wich formula convert hFe to ß-eta?
thanks advance
zlatko

 

[Audioguru]

bjt hfe

HFE is beta. It changes with each transistor even if they have the same part number because it is a range. Some transistors have a high beta and others have a low beta. See the range on the datasheet for a transistor.
Beta is the current gain, not the voltage gain of a transistor.

Beta is affected by the amount of current and how many volts there is from collector to emitter, Temperature also affects it.

 

[xulfee]

transistor hfe definition

both terms r same

Added after 1 minutes:

there is just difference in doing analysis,i mean some where we call it Hfe & some where we call it beta

 

[FvM]

hfe beta

It should be noticed, that the shortcuts for BJT current gain are not totally uniform in literature. Generally a DC (large signal) and a small signal current gain are existing as different parameters. It's almost accepted, to use hFE as designator for DC and hfe for small signal gain. Usage of β is more varying, although it's mostly used as hFE synonym in English-language literature. But Gray/Meyer e. g. uses a β0 for small signal current gain and in german literature, β traditionally means small signal in contrast to B for DC gain.

Many data sheets are trying to avoid possible misunderstandings by using verbose parameter definitions in any place.

 

[zlatkoMM]

hfe definition

Hi again...
FvM is in right hFE is SMALL SIGNAL CURRENT GAIN mesured on 1kHz
and ß (beta is CD current gain.So im from europe and i know that we learn in high
school that is not the same thing.
Whatever ordinary multimeter measure ß no mather what is written (hFe).OK
bye
regards
zlatko

 

[LvW]

hfe and beta

To be correct by 100% (and to increase the confusion) I like to point out that there is still a difference between hfe and β.

- The small signal current gain (sometimes called β) equals the ratio ic/ib under operating conditions, and
- hfe is a so called "4-pole parameter" and is defined as ic/ib for uce=0 , which means that the signal voltage between collector and emitter is zero (ac short circuit).

But in practice, this difference can be ignored.

 

[Audioguru]

hfe transistor definition

Some people are saying things in this thread that are wrong.
hFE is DC current gain.
hfe is AC current gain.
The datasheet of a 2N3904 transistor by Fairchild proves it.

 

[LvW]

beta hfe

Some people are saying things in this thread that are wrong.
hFE is DC current gain.
hfe is AC current gain.
The datasheet of a 2N3904 transistor by Fairchild proves it.

Hi Audioguru,

Don´t believe everything you find in datasheets. I recommend to go back, instead, to the definition. May I direct your attention to the fact, that the data sheet you have posted gives the frequency (1 kHz) for the measurement of the parameter which Fairchild calles "hFE". Therefore, I don´t think that it can be the DC current gain.

And more than that, the vertical axis is named with "hfe". Therefore, FAIRCHILD proves nothing !

 

[Audioguru]

bipolar hfe

Fairchild spells out the hFE as DC current gain.
It shows a graph for hfe at 1kHz which is AC, not DC.

 

[FvM]

bjt hfe beta

Yes, the Fairchild datasheet fragments show the common usage of hFE and hfe. It got a bit confused by the unrelated text copied above a diagram, that hasn't to do with DC gain. Although they had been mixed up in some above contributions, the definitions are undisputable so far, I think.

I also like to emphasize, that a datasheet can't prove anything. Furthermore, the definition of a term as such can't be right or wrong, at best corresponding to the common usage in a particular science or application field. There is definitely a different usage of β.

 

[LvW]

hfe of bjt

Fairchild spells out the hFE as DC current gain.
It shows a graph for hfe at 1kHz which is AC, not DC.

I don´t care about Fairchild.
Instead, I know that the letter "h" is used worldwide to characterize the 4-pole-hybrid-parameters (hybrid>>h) which undoubtly are small signal ac parameters. That´s a fact.
Of course, there is absolutely no difference between "hfe" and "hFE" - it´s simply a kind of typing error, which can be found very often in datasheets.

 

[Audioguru]

hfe for bjt

My Philips 1968 silicon transistors databook agrees with Fairchild.
hFE is DC current gain and hfe is AC current gain.
Motorola also agrees.

 

[FvM]

hfe of a bjt

Of course, there is absolutely no difference between "hfe" and "hFE"

I agree with Audioguru in so far, that in the English-language literature hFE and hfe are apparently used to distinguish DC (large signal) and small signal gain, particularly in any data sheet. I don't know however, where this usage comes from.

 

[House_Cat]

bipolar hfe

Sorry FvM, you are wrong. hfe and HFE are two different, but related, characteristics of a bipolar transistor.

hFE is the short circuit (vCE=0) forward current ratio (also known as h21) at a specified DC bias (which must be stated for each value of hFE).

hfe is the small signal AC gain at a specified bias, and is frequency dependent. The frequency and bias for the stated hfe should be specified in the datasheet.

In low frequency circuits, the small signal AC and DC gains are so close in value, they are frequently used interchangably.

The use of lower case letters to represent AC values is an IEEE convention, not a typographical error.

 

[laktronics]

hfe transistor

Hi,

Highly confusing definitions in deed!!!

hFE is the short circuit (vCE=0) forward current ratio (also known as h21) at a specified DC bias (which must be stated for each value of hFE).

WHOEVER HAVE DEFINED IT, MY LITTLE BRAIN IS UNABLE TO UNDERSTAND:

1. When vCE =0, how can you 'specify DC bias'?

2. At vCE=0, what will be the forward current ratio, as per data sheet?

Regards,

 

[zlatkoMM]

transistor beta hfe

LvW is right i find book from my high school :
hFE is 4-pole-hybrid-parameters (hybrid>>h) which undoubtly are small signal ac parameters. (dinamic parametars).

WOW sach a disqusion !!!!!!!!!!

 

[FvM]

hfe dc current gain

Well, I didn't claim to have the right definition, I just reported a common usage in literature. It may be contrary to others and dubious considering the scientific background, that LvW and House_Cat referred to.

But it's a fact, that hFE is used for DC current gain in many places, and not only as a typo. That's very different to the usage House_Cat quoted.

I reviewed some old datasheets and databooks. Valvo e. g. used B for DC current gain and h21e or β for small signal (AC) gain in the ancient German language data sheets. As the datsheets were translated (when the traditional Valvo brand and their products moved to Philips), the DC current gain symbol B was replaced by hFE and is used up to now.

Generally, anyone who thinks he has to decide about wrong or right in this matter should calm down and consider, that this isn't an applicable category in term definition. It is at most meaningful, when a teacher or lecturer demands to follow the term usage of his class with the tests. And furthermore, a term definition is obviously inappropriate (or wrong), when it's misunderstood by the audience. Or it's the wrong audience...

 

[LvW]

definition hfe

Yes, I think we all should and can agree with FvM.
And in the mean time I have convinced myself that, indeed, the term hFE sometimes is used for the DC current gain (common emitter configuration).
I am a bit unlucky about this, since it can (and has) lead to misunderstandings because the letter "h" originates from the "hybrid 2-port small signal" model of the BJT, which implies that there is a "signal".
Anyway, it´s all not too important because the difference between β, B, hfe, hFE, h21,....is and can be neglected for most real circuits.

 

[House_Cat]

what is hfe bjt

1. When vCE =0, how can you 'specify DC bias'?

2. At vCE=0, what will be the forward current ratio, as per data sheet?

Sorry I confused you. I tried to jam too much into one sentence.

DC bias, when discussing hFE, is the base-emitter current IBE. When the transistor is saturated, vCE for the ideal transistor is zero. hFE is the ratio of collector current to base current (iCE/iBE). The transistor can be saturated for many values of iBE above the saturation bias - that is why the datasheet will tell you what bias current existed at the point where hFE was defined.

 

[Audioguru]

transistor hfe beta

The current gain spec for a transistor never has it saturated. it always is linear with 1V to 10V of collector to emitter voltage.

The datasheet spec's a saturation voltage loss when the base current is much higher than the current gain would indicate.