Guitarfreak, post: 352126 wrote: I see what you mean, I was trying to calculate the Resistor values last night and I realized that without more information it doesn't work. I should be using Ohm's Law right? V=IR. What do you use for the current value?

Current is the choice of the designer and is primarily dependant on what the peak load current is expected to be. The collector current cannot be below that otherwise you will never be able to fully drive the load as specified. This seems to be something that was overlooked in the confidence booster supplied with the lower value trimmers....

Boswell, post: 352124 wrote: By the way, the bias for a transistor is specified in terms of current and not voltage, so you are doubly dependent on the resistor values at the input and battery voltage to get this particular design to behave in an acceptable fashion.

I just wanted to point out that while this is quite correct, this should not be read as a transistor being current operated. This is a common misconception (hence this post) and I would like to make it abundantly clear that a transistor is a transconductance device with the collector current being (exponentially) dependent on it's Vbe. I think that is about as far as is practical to go on this forum!

Assuming we are talking about a common emitter transistor gain stage. Since gain is higher with a bigger resistor on the collector and a smaller resistor on the emitter, how is gain calculated when the emitter resistor is removed and jumpered. Something tells me this brings limits into the equation. And I hate limits.

To be honest, I find you asking a question about seemingly every little thing that occurs to you is asking a bit too much. If you read the reference I gave you in your other thread asking these sort of questions, you can find the answers. I'm sorry but I just don't have the time to answer everything you ask. Maybe someone else does!

Sorry if my first response was a bit terse but if you really want to learn more about electronic design then personally I don't think recording.org is intended for this. It of course is up to the mods to decide what is appropriate and any response is up to individuals. While I will try to help with the odd question, you can not seriously expect me (or others) to give you a comprehensive response every time you have a brainstorm.

With regard to the link I gave in your other thread, I got a response from the guy who effectively agreed with the points I raised with him but literally said it was convenient to "pretend" that a transistor was a current operated device. Not the highest integrity shown then!

Having said that, although the site is intended to be basic, it should be enough for you to find out what the limit is on gain. Take some of the stuff with a pinch of salt though as the approximations used there are not revealed. What you should also consider is that voltage gain is one thing and power gain another, in other words the impedance at any point in a circuit should be considered.

Of course a single transistor is not capable of infinite gain as you surmised. Clue: there is Re and re in the emitter circuit and you cannot reduce re to zero.

Well I am asking the forum, not you individually, which is why you did not receive this message in PM form. Do not feel obligated to respond if you feel it is not your responsibility to do so. With that said I will never stop asking questions, the only stupid question is one which remains within.

Well I'm glad you appreciate the effort I have gone to so far!

I've given you links that I believe will be far more useful to you and the advice I've given is only intended to help you improve your knowledge. I just don't think you will be best served by constantly asking this type of question in this particular forum - it's called recording.org not electronicdesignbasics.org! Sometimes you will just have to work out answers for yourself and when you do you will learn far more effectively.

Of course you can ask your questions here, I'm not disputing that and I may also choose to answer you, but is this really the best place to be getting the answers or knowledge you are seeking?

Good luck.

Guitarfreak, post: 352421 wrote: Assuming we are talking about a common emitter transistor gain stage. Since gain is higher with a bigger resistor on the collector and a smaller resistor on the emitter, how is gain calculated when the emitter resistor is removed and jumpered. Something tells me this brings limits into the equation. And I hate limits.

Hey there GF....
I'm certainly not trying to take sides on this...but..
There's not a whole lot for you to assume in terms of a transistor circuit...they are what they are and understanding how they actually work is all part of understanding electronics as a whole. You aren't inventing anything new....or going to discover something new....you really only need to learn the rules....they are all well understood....there are ranges of correct operation given a particular transistor type.
Here's a cool site with a very intuitive explanation about transistors with a gain calculator....I hope it helps...

[[url=http://[/URL]="http://www.bcae1.co…"]Transistor Example[/]="http://www.bcae1.co…"]Transistor Example[/]

Adding additional stages of transistor amplification and coupling one stage to the other is another topic of comprehension once the concept of a single transistor stage is well understood. Op-Amps are the new analog transistor chip device....they integrate multiple transistor stages within a single profile that allows more complex applications to be more easily designed without the need to futz around with individual bias, gain and coupling issues required by discrete single stage designs.
I believe Mr. Ease was trying to point that out....
And finally, I'm sure you're having fun learning all of these technical attributes of electronics itself....it's not always easy to comprehend....some people never get it!
But don't get discouraged and keep listening to your audio with your ears and keep playing that guitar and over time read as much as you can stomach on the electronics and realize that it is a prescribed science that needs to be studied and understood and eventually the guessing and assumption go away....it really isn't magic!....it just seems that way to the uninformed....

djmukilteo,

I don't see this as "sides" rather than finding the best way to help Guitarfreak. In post #44 he asked a question that had effectively already been answered in posts #39 and #41 as well as in the link I gave. If he seriously wants to understand transistor operation I'd be much happier helping if I felt that the help vttom and I have already given was getting through. It serves no purpose asking further questions if the information already given is not understood. By all means he should ask if what we have explained is not understood but it seems at the moment to have been completely ignored.

I don't see that spoonfeeding answers is ever going to help - I think GF needs to put more thought into the information he is getting before asking questions that overlook the info he already has.

MrEase, post: 352508 wrote: djmukilteo,

I don't see this as "sides" rather than finding the best way to help Guitarfreak. In post #44 he asked a question that had effectively already been answered in posts #39 and #41 as well as in the link I gave. If he seriously wants to understand transistor operation I'd be much happier helping if I felt that the help vttom and I have already given was getting through. It serves no purpose asking further questions if the information already given is not understood. By all means he should ask if what we have explained is not understood but it seems at the moment to have been completely ignored.

I don't see that spoonfeeding answers is ever going to help - I think GF needs to put more thought into the information he is getting before asking questions that overlook the info he already has.

Totally agree MrEase....my use of the term "sides" wasn't really appropriate, I was just trying to begin my comment to GF in a nice non-confrontational way and it looked like you two were maybe getting off track....
I know GF is much more interested in guitar tone and his recording efforts...and the electronics can be daunting and easy to stray off in wild assumptions. I'm pretty sure GF's latest attention, ideas and questions have come from guitar effects boxes, which is a great application of audio electronics. I hope he continues to read about the basics of electronics even if his school is not providing the most coherent information.
The internet is a wealth of info as you and I have pointed out and I would hope GF focuses on the sites related to guitar electronics which will help him in his quest!

Why not build a box utilizing germanium transistors instead of silicon? There is a difference in the sound you know? Maybe you don't know? And they are not interchangeable because of a difference in voltage drop with silicon. But fatter, warmer may be the result of utilizing germanium transistors.

My first powerless radio
Mx. Remy and David

djmukilteo, post: 352510 wrote: Totally agree MrEase....my use of the term "sides" wasn't really appropriate, I was just trying to begin my comment to GF in a nice non-confrontational way and it looked like you two were maybe getting off track....
I know GF is much more interested in guitar tone and his recording efforts...and the electronics can be daunting and easy to stray off in wild assumptions. I'm pretty sure GF's latest attention, ideas and questions have come from guitar effects boxes, which is a great application of audio electronics. I hope he continues to read about the basics of electronics even if his school is not providing the most coherent information.
The internet is a wealth of info as you and I have pointed out and I would hope GF focuses on the sites related to guitar electronics which will help him in his quest!

Thank you for understanding where I am coming from! See I knew I had friends here. The more I learn about circuits from playing with them (which is dismal at best it seems) the more 'gray' a term like 'gain' becomes. It seems that gain can come from anywhere and choosing from a cocktail of variables tailors the resulting gain's sound. IDK, there is something about transistors that I like. The fact that it seems that you have more control over what the resulting sound is appeals to me, whereas with an IC I haven't got a clue what is going on inside the chip and it seems that the resulting sound is derived from the chip itself.

RemyRAD, post: 352513 wrote: Why not build a box utilizing germanium transistors instead of silicon? There is a difference in the sound you know? Maybe you don't know? And they are not interchangeable because of a difference in voltage drop with silicon. But fatter, warmer may be the result of utilizing germanium transistors.

My first powerless radio
Mx. Remy and David

I've been planning on doing some experimentation with these things as variables. I have heard that germaniums are gainier but that they color the sound more. Also that they are tempermental and changes in temperature or humidity may change the way they sound. I do like the way that the Dallas Arbiter Fuzz Face sounds and that uses germanium transistors, and it seems that that pedal is if anything more transparent and less gainy. It must have a lot to do with the way the circuit is set up. I don't know, I don't believe everything that I read.

RemyRAD, post: 352513 wrote: Why not build a box utilizing germanium transistors instead of silicon? There is a difference in the sound you know? Maybe you don't know? And they are not interchangeable because of a difference in voltage drop with silicon. But fatter, warmer may be the result of utilizing germanium transistors.

My first powerless radio
Mx. Remy and David

Absolutely!....and hey what about the original transistor....a tube (or valve) as they're called across the pond...a little more voltage to be wary of...but all is available and out there for experiments GF...I think if you focus your study and understanding of the basic amplifier stage that will take you a long way! Hang a few resistors and caps on there and be careful and study the circuits that are out there. And don't be afraid of opamps they are very powerful IC's that can do many things with analog designs...they were devised to BE the "amp" with a handful of resistors and capacitors they become the building block for more complex circuits...

I think we should try to get GF biasing a silicon transistor properly before we confuse the issue with germanium leakage currents!

MrEase, post: 352545 wrote: I think we should try to get GF biasing a silicon transistor properly before we confuse the issue with germanium leakage currents!

How exactly do you suggest I do this? What to buy and how.

Don't buy anything yet, read first....
http://eece.ksu.edu/~wkuhn/useful_stuff/BJTbiasing.PDF

Holy shit, that explains the abbreviations that I wasn't getting with the formulas before. Will give her a good read, thanks.

I had a quick look and it only gives you some of what you have been asking about. I'd second Link555 and say that you don't need to rush out and buy anything - google is your friend here together with the links I and others have given you - but even better would be to get down to your local library and search out books on electronic design - certainly I'd find something that suits you before buying. As I've said before, I don't believe you can really learn about electronics hereabouts but there is plenty of info on the net and there is no alternative to working through all the explanations available until you really start to understand what is happening. I'd also suggest looking up Norton and Thevenin equivalents to go with Kirchoff's law etc as you will also need to understand some electronic network theory too.

I mentioned a while ago about what is referred to as re (as opposed to Re). This is what limits the voltage gain together with the total collector load resistance. Re is the physical emitter resistor whereas re is intrinsic to the transistor. re varies with collector current and is calculated normally like this:

re = 25/Ic where Ic the collector current is in mA. In the example of your confidence booster I estimated Ic as 0.5 mA (although the biasing scheme is not great!) hence re will be 25/0.5= 50 Ohm. This is in series with the real Re and is what limits gain when Re is reduced to zero.