Leakage in germanium transistors - terminology question

[gmr1]

I've recently gotten the chance to use a DCA55 to check the gain and leakage in a pile of germanium transistors I've had for awhile. I see acceptable leakage quotes usually made in "uA" on this forum, but this meter returns leakage current readings in mA. What is the conversion for these two numbers? I'm pretty uneducated when it comes to unit of measure, so I hope this isn't a stupid question!

What is a typical acceptable range in mA to look for? The AC128's I have are all over the map (in both gain and leakage).

Thanks!

- Greg

[R.G.]

"uA" stands for "micro ampere" and "ma" stands for "milli ampere".

"Milli" is the prefix for "one-thousandth" and "micro" is the prefix for "one-millionth", so a milliampere (ma) is one thousand microamperes (uA).

If you do electronics for any length of time you'll get really familiar with such measures. See the FAQ.

My personal rule of thumb is that if a small signal Ge transistor leaks more than 300uA (MICRO-amperes) then it's too leaky. The more leakage current, the less reliable in general the transistor is my experience. Other people may try to squeeze a month (year... decade) out of a leaky device. To each his own.

That's one-third of a milliampere. (ma).

[Papa_lazerous]

I have a DCA55 they are good toys best purchase I made for a while

[gmr1]

R.G. - Thanks for the explanation. I didn't know what uA and mA stood for, so I was having a hard timing figuring it all out with a google search.

Here's another question - other than the specifications (gain, leakage, etc), what makes one transistor model much more sought after than another? Are different models of transistors originally designed to be "voiced" differently?

Papa_lazerous - the DCA55 is a lot of fun to play with. Seems like a very handy tool.

[Papa_lazerous]

AMongst other things, stuff that affects how transistors are sought after......

1st mojo!! people get crazy about a certain part number sometimes as its the same as the original that doesnt mean it sounds best it may have just been cheap at the time
2nd Transistors are not all created equal, they are designed with an application in mind, and they might be very good at high frequencys or low or whatever. but a transistor is not a transistor for the aake of it
3rd Germanium and silicone behave very differently, for example you know Ge have a much small diode drop on them than Si, Ge also tend to act differently when they go out of their linear range, they tend to squish and compress the signal slightly when you start going too far with them, where as Si tend to be more abrubt and clip sooner.  Also they add different "colour" to the sound Ge are a little less precise as transistors are concerned but the results are often pleasing to the ear

RG will have a better explanation I am sure

[R.G.]

I'm not sure there's a whole lot to add to that. You got the right points, and in the right order. In marketing, it's always mojo first, reality last.