Component grades

[Jules]

Hi All, I have been building some pedals that require BC549c transistors (shark fin and Weener wah). tayda only has BC549b, I understand that they have less gain than the bc549c, are they generally OK to use?
It is the same with bc108 and bc109 transistors, only available in 'b' type from Tayda.
I am in Australia so don't order through smallbear etc often to save delivery fees.
Thanks
Jules

[TGP39]

Hi Jules.  I found this description on www.petervis.com. Since you already know about the gain differential and since the pinouts are the same between the b and c version, you should have no problem substituting one for another. Here is more info....

The BC549C is an NPN transistor belonging to a group of general-purpose NPN semiconductors consisting of BC547, BC548, and BC549. These transistors are utilised in audio frequency, and small signal directly coupled preamplifiers.

The general-purpose range of transistors is a good substitute for basic non-critical audio applications, as these transistors are similar and equivalents to each other.

These transistors are the direct modern equivalent replacements to the earlier BC107, BC108, and BC109. The most noticeable difference is in the packaging and pin configuration. The BC109 package was TO-18 / SOT18 metal canister, whilst the modern BC549 package is a TO-92 / SOT54 plastic material.

Pinout

The pin configuration is very simple and is collector, base, emitter.

BC549B Vs BC549C
The BC549 series subdivides further into two groups B, and C. This suffix indicates the current gain.

With Vce at 5 V, and Ic at 10 µA, the current gain (hFE) for B is typically 150, whilst for C is 270.

With Vce at 5 V, and Ic at 2 mA, the current gain (hFE) for B is typically 290, whilst for C is 500.

With Vce at 5 V, and Ic at 100 mA, the current gain (hFE) for B is typically 200, whilst for C is 400.

As you can see from this, the largest current gain is available from group C that is why the BC549C is more commonly used.

Hope this helps you.....

Steve.

[jimilee]

I'd get the bc549c, you can sub the b until you get some. I noticed a difference in a wah that I built. I don't remember which one though....


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[gtr2]

Also...Tayda transistor gains are really inconsistent.  I'd recommend a different supplier for them...IMO

[Jules]

Thanks all for the replies.
Thanks to TGP39 for the comprehensive report.
Jules