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Which is BC547, BC547B or BC547C among them? Confusing lot!

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Willen

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I know these all transistors has different hFE:
547
547A
547B
547C

And this different hFE may affect the bias on critical circuitry. I have few transistors but can't read its value correctly which is confusing me!
 

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1st transistor has different type of TO-92 packaging case.

4th and 5th unknown transistors are here:
 

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I have no idea what you're asking.

Every single transistor has a different gain. Even if they have the same model number. Sure, they often have the same average hfe, but it will always be a little off.

There is no such thing as a "different type of TO-92 packaging case". A TO-92 is a TO-92. The only difference between the first one and the other two is the way the pins are bent. That has nothing to do with the packaging.

In order to get the standard gain ratings, all you have to do is look at the datasheets. Remember, google is your friend.
 
Except for those that "test" the semiconductor device, circuits of same TYPE are designed to perform equally well irrespective of variations in Device Parameters. Gains, Frequency response, etc. are decided by passive devices rather than active devices.
( I define TYPE like "Audio/RF Preamps", Audio/RF Power Amps", IF Amps, Video Amps", etc.)

Ramesh
 
There is no such thing as a "different type of TO-92 packaging case". A TO-92 is a TO-92. The only difference between the first one and the other two is the way the pins are bent. That has nothing to do with the packaging.

However, they do have different pinouts. **broken link removed**

Mike.
 
Ops! Great mistake on 4th and 5th transistor!

Mistakely I wrote 457! Please read them- '547'
 
I mean:- I have a critical circuit made by '1st' type of transistor and it's working. If I replaced 1st transistor with 2nd or 3rd one, the circuit might be fail. I think '547' has large range of hFE (100 to 800) but '547B' or '547C' has small range of hFE like 100 to 300 or 400 to 600.

I going buy these transistor by knowing which is 547, 547A, 547B and 547C. So :)
 
BC5xx are terrible for pinouts. Every time you grab one from the junkbox it will have a different pinout.

It's better to buy bags of 100 in more modern transistors. I like BC337 NPN, and BC327 PNP. They are better than BC547; higher current, better gain etc. They always have the new modern standard pinout.

Hobby shops also sell 100 bags of general purpose small signal transistors, I think the new part numbers are PN100 NPN, and PN200 PNP. These also have the new standard pinout.
 
A good circuit design should in general be able to accept a transistor with a wide hfe range, by choice of a suitable bias arrangement. What bias arrangement do you have? Can you modify it to reduce the sensitivity to gain variation?
 
BC5xx are terrible for pinouts. Every time you grab one from the junkbox it will have a different pinout.

It's better to buy bags of 100 in more modern transistors. I like BC337 NPN, and BC327 PNP. They are better than BC547; higher current, better gain etc. They always have the new modern standard pinout.

Hobby shops also sell 100 bags of general purpose small signal transistors, I think the new part numbers are PN100 NPN, and PN200 PNP. These also have the new standard pinout.

Hola RB,

Talking about standards, is that new modern standard really standard as standards were expected to be and never were? I am not playing with words.

I realized that standards are such a thing for those who consider them like that and nothing else.

Probably around a year ago I posted about a transistor having E and C reversed (vis a vis some particular standard pinout). The prevailing reply in three different forums was something like "always check the pins before soldering). Learnt my lesson.

As a surveyor I learnt how many "standards" do exist to qualify rust on steel cargoes. A long list. I am tempted to create mine. Why not after all?
 
I use only Philips/NXP and Motorola/ON Semi BC547B transistors. They are clearly marked BC547A (low current gain), BC547B (medium current gain) or BC547C (high current gain).
The BC337 are also available with selected groups of current gain but it is marked "-16" for an average gain of 160, "-25" for an average gain of 250 and '-40" for an average gain of 400 at 100mA.
 
A good circuit design should in general be able to accept a transistor with a wide hfe range, by choice of a suitable bias arrangement. What bias arrangement do you have? Can you modify it to reduce the sensitivity to gain variation?

look this one. This is working with 1st C547B transistor. Don't know how to modify for other transistor of 547
 

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Q1 is the gain-critical transistor in that circuit. Here's how I would modify its bias to reduce the sensitivity to gain variation:
BiasMod.gif

Edit: Depending on the characteristics of your piezo element you might want to boost the Q1 stage gain by connecting a ~ 10uF cap in parallel with the emitter resistor R13.
 
A BC547 transistor has an hFE from 110 to 800.
I calculated the bias point of the preamp transistor with a good hFE of 505, a low hFE of 109 and a high hFE of 807.
The transistor with low hFE might not work well in that circuit so a BC547B or BC547C should be used.
 

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A BC547 transistor has an hFE from 110 to 800.
I calculated the bias point of the preamp transistor with a good hFE of 505, a low hFE of 109 and a high hFE of 807.
The transistor with low hFE might not work well in that circuit so a BC547B or BC547C should be used.

-'BC547 has 110 to 800 hFE' mean some 547 might has 110 and some 547 might has even 800? Not fixed?

-Then which is the (aprox.) suitable feedback resistor value for low hFE transistor?
 
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Hola RB,

Talking about standards, is that new modern standard really standard as standards were expected to be and never were? I am not playing with words.
...

I'm no expert on standards, but from experience I can say in the 1970's when I started building with electronics and using BC5xx transistors, everyone you would pick up had a different damn pinout. Even when I would buy 10 or 20 at a time from the parts drawer at the electronics shop they were all different.

It was an absolute pain!

These days TO-92 pack transistors (and the few manufacturers who still make through hole transistors) seem to have standardised pretty well on the CBE pinout (looking from the front).

I'm just guessing of course, but I think it's a move towards deliberate "standardising", after all, bipolar transistors in SMD packs all have standard pinouts, so why not try to stick to a standard on through-hole bipolars now too?
 
These days TO-92 pack transistors (and the few manufacturers who still make through hole transistors) seem to have standardised pretty well on the CBE pinout (looking from the front).
Only for European BCxxx transistors. American 2Nxxxx TO-92 case transistors are the opposite with the pins as EBC.
 
-'BC547 has 110 to 800 hFE' mean some 547 might has 110 and some 547 might has even 800? Not fixed?
A BC547 transistor can have an hFE between 110 and 800.
A BC547A is selected to have an hFE between 110 and 220. A BC547B is selected to have an hFE between 200 and 450.
A BC547C is selected to have an hFE between 420 and 800.

Then which is the (aprox.) suitable feedback resistor value for low hFE transistor?
It is easy to calculate the feedback/bias resistor value. Since the supply is 12V then set the collector voltage at 6.0V and calculate the resistor if you know the hFE number.
 
Even different transistors with the same type number will have a range of hfe values. A bias resistor somehere in the range 200k-400k should do for hfe ~110. Bear in mind too that the operating point of the transistor will vary with temperature, especially when only a single base-bias resistor is used.
 
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