What exactly is emitter degeneration anyhow?

[SteveThackery]

In the end, to validate their intelligence you get people like KE5FX and SteveThackery - who probably didn't read anything of what has been discussed here - supporting irrelevant visions backed up with some smart sounding quotes posted by MrAI.

What the HELL?  This totally misrepresents my contributions to this thread.  My first contribution was a lengthy post answering the OP's question in a way which I tried to make simple and intuitive explanation of emitter regeneration.  It was thanked by the OP.  My second contribution was a passing comment on the value of book-learning.

I can only think you must be referring to my third post:

"A person's knowledge and beliefs form part of their identity, so embracing new, contradictory knowledge requires giving up part of that identity. It requires you to accept that you were wrong about something for years. Both are extremely hard to do."

That is a philosophical statement, based on my personal experience, about why humans seem to be resistant to change, especially resistant to changing their ideas.  I was emphatically NOT taking sides in this pathetic willy-waving debate, about which I don't give a fuck.

It was a passing comment, that's all.  And by the way, I totally stand by it, even though it's an aside to the main debate.

I detest people misrepresenting my words or my position.  You owe me a big apology - are you big enough to give it?

[magic]

take this post from you:
https://www.eevblog.com/forum/beginners/what-exactly-is-emitter-degeneration-anyhow/msg5735353/#msg5735353

Which I quote here:

In the attachment, we can see the plots for the three models.  Since the single resistor model (green line) was the only one that came into question, I mapped out the region of validity with the light gray horizontal and vertical lines.   The best place is within the square formed by all four of the light gray lines.
We can note that outside that range it's not going to be very good, but inside, it's not too bad.  It has the benefit of not having to explain what the calculus definition of dv/dt is which may not yet be part of the coursework.  It can certainly be called an oversimplification, no doubt there.  The question is, did it have any uses.  Well, the answer to that has to be that it has very limited use, that's probably why the complaint came in

Is it this plot?

I can't help but notice that there is a much simpler and more accurate approximation of Vf inside that gray box: just assume it doesn't depend on If at all.
 

[MrAl]

take this post from you:
https://www.eevblog.com/forum/beginners/what-exactly-is-emitter-degeneration-anyhow/msg5735353/#msg5735353

Which I quote here:

In the attachment, we can see the plots for the three models.  Since the single resistor model (green line) was the only one that came into question, I mapped out the region of validity with the light gray horizontal and vertical lines.   The best place is within the square formed by all four of the light gray lines.
We can note that outside that range it's not going to be very good, but inside, it's not too bad.  It has the benefit of not having to explain what the calculus definition of dv/dt is which may not yet be part of the coursework.  It can certainly be called an oversimplification, no doubt there.  The question is, did it have any uses.  Well, the answer to that has to be that it has very limited use, that's probably why the complaint came in

Is it this plot?

I can't help but notice that there is a much simpler and more accurate approximation of Vf inside that gray box: just assume it doesn't depend on If at all.
 

Hi,

Yes sure, and for the model not shown you can simply draw a straight horizontal line that intersects the Y axis at v=0.7 volts.  That's another model that is used time and time again.  It assumes that the voltage is always 0.7 volts no matter what.

There are better models, and even better than that exponential curve indicates.  They are all approximations, and we use whatever approximation works, as long as it works for what we need it to.  The exponential model is rarely used in hand calculations because it's much more complicated, and when you have more than one diode you have to do some nasty numerical solution to get the right result.  It can be fun though, unless you don't like math.

[tggzzz]

In the end, to validate their intelligence you get people like KE5FX and SteveThackery - who probably didn't read anything of what has been discussed here - supporting irrelevant visions backed up with some smart sounding quotes posted by MrAI.

What the HELL?  This totally misrepresents my contributions to this thread. 
...
I detest people misrepresenting my words or my position.  You owe me a big apology - are you big enough to give it?

Temperance's post was very badly worded w.r.t. exactly who he was referring to at each point.

However, my (speed?) reading of it was that he was showing MrAl a LART, not showing you one. In that view of the world, I can agree with both Temperance and your earlier posts.

[MrAl]

MrAI,

take this post from you:
https://www.eevblog.com/forum/beginners/what-exactly-is-emitter-degeneration-anyhow/msg5735353/#msg5735353

Which I quote here:

In the attachment, we can see the plots for the three models.  Since the single resistor model (green line) was the only one that came into question, I mapped out the region of validity with the light gray horizontal and vertical lines.   The best place is within the square formed by all four of the light gray lines.
We can note that outside that range it's not going to be very good, but inside, it's not too bad.  It has the benefit of not having to explain what the calculus definition of dv/dt is which may not yet be part of the coursework.  It can certainly be called an oversimplification, no doubt there.  The question is, did it have any uses.  Well, the answer to that has to be that it has very limited use, that's probably why the complaint came in

You admit yourself that the oversimplification is only valid over a very limited range and it's use is very limited. And here I think you have to admit that the size of the rectangle for which the approximation is good enough becomes smaller and smaller with decreasing bias current to the point of unusable well before the diode forward voltage falls below the knee voltage and vice versa. Those are the things you fail to mention. Instead you choose a bias point where the approximation is reasonably valid in a tiny rectangle to prove your point. I think this is misleading and should only be used by people with experience who developed a solid understanding of what is going on to understand where the oversimplification falls apart. Or in other words: how is someone without experience able to tell when the model falls apart? They don't . When people confront you with that you revert to insulting people in here several times by calling them species of substandard intelligence who fail to lean something from what you have to offer. And till today you continue do so.

You then go on to state that your Vf / If oversimplification avoids complicated math and is as such easier to understand while all that is required is calculating ΔVf / ΔIf at a few points. That's not difficult at all and doesn't require any calculus. Neither does the ΔVf / ΔIf  simplification fall apart over a very wide range above the diode knee voltage. (You demonstrated this in an other post.)


In the end, to validate their intelligence you get people like KE5FX and SteveThackery - who probably didn't read anything of what has been discussed here - supporting irrelevant visions backed up with some smart sounding quotes posted by MrAI.

But maybe I've spend to much time reading "the art of being right" written by your favorite author.

Hello again,

So, you explain to me that I've insulted some people, by you yourself insulting some people.  You actually even mentioned them by name.  Does that sound right to you?

You have to be careful how you interpret things said, they are not always to be taken in the negative sense.  For example, by saying that intelligence plays a part in understanding a certain concept, it does not mean that people who do not understand it yet are stupid.  For one thing, we all have to learn when presented with ideas we never heard of before.  That does mean that we are ignorant of that concept to start with, but that does not mean we boil it down to we are stupid as an absolute, never-ending phenomenon.  Once we learn that concept we then have that under our belt.
So in most cases we are just acting stupid, not entirely stupid for all time.
Also, by stating something about intelligence it could be an attempt to get people to think about it more carefully, then they might attempt to learn the concept.  A typical dialogue: "John-Boy, you are acting so stupid right now!"

Actually, I don't think anyone here is stupid in the absolute sense, but some may be more stubborn than others.  I can be stubborn sometimes too, but I've learned that it's best to consider new ideas than to knock them.

This is a topic we should really take to PM's though it's not helping the OP I don't think.  The OP wanted something simple and understandable and has little interest in the behavior of people in forums.

[MrAl]

In the end, to validate their intelligence you get people like KE5FX and SteveThackery - who probably didn't read anything of what has been discussed here - supporting irrelevant visions backed up with some smart sounding quotes posted by MrAI.

What the HELL?  This totally misrepresents my contributions to this thread. 
...
I detest people misrepresenting my words or my position.  You owe me a big apology - are you big enough to give it?

Temperance's post was very badly worded w.r.t. exactly who he was referring to at each point.

However, my (speed?) reading of it was that he was showing MrAl a LART, not showing you one. In that view of the world, I can agree with both Temperance and your earlier posts.

Actually he seemed to be addressing a MrAI, and that's not me

[MrAl]

Here's another interesting quote I found written by Frederic Crews:

"General rationality requires us to observe the world carefully, to consider alternative hypotheses to our own hypotheses, to gather evidence in a responsible way, to answer objections. These are habits of mind that science shares with good history, good sociology, good political science, good economics, what have you. And I summarize all this in what I call the “empirical attitude.” It’s a combination of feeling responsible to the evidence that is available, feeling responsible to go out and find that evidence, including the evidence that is contrary to one’s presumptions, and responsibility to be logical with one’s self and others. And this is an ideal that is not so much individual as social. The rational attitude doesn’t really work when simply applied to one’s self. It is something that we owe to each other."

I like the last line best.

[temperance]

In the end, to validate their intelligence you get people like KE5FX and SteveThackery - who probably didn't read anything of what has been discussed here - supporting irrelevant visions backed up with some smart sounding quotes posted by MrAI.

What the HELL?  This totally misrepresents my contributions to this thread.  My first contribution was a lengthy post answering the OP's question in a way which I tried to make simple and intuitive explanation of emitter regeneration.  It was thanked by the OP.  My second contribution was a passing comment on the value of book-learning.

I can only think you must be referring to my third post:

"A person's knowledge and beliefs form part of their identity, so embracing new, contradictory knowledge requires giving up part of that identity. It requires you to accept that you were wrong about something for years. Both are extremely hard to do."

That is a philosophical statement, based on my personal experience, about why humans seem to be resistant to change, especially resistant to changing their ideas.  I was emphatically NOT taking sides in this pathetic willy-waving debate, about which I don't give a fuck.

It was a passing comment, that's all.  And by the way, I totally stand by it, even though it's an aside to the main debate.

I detest people misrepresenting my words or my position.  You owe me a big apology - are you big enough to give it?

If I'm wrong I'm not afraid to admit being wrong at all. In my interpretation I didn't see what you wrote as a passing comment but taking sides. So I apologize for accusing you of such.

[SteveThackery]

If I'm wrong I'm not afraid to admit being wrong at all. In my interpretation I didn't see what you wrote as a passing comment but taking sides. So I apologize for accusing you of such.

Thank you, @temperance.  All is well. 👍😁

[KE5FX]

Temperance's post was very badly worded w.r.t. exactly who he was referring to at each point.

I think he insulted me, but if so, it was an unusually easy one to shrug off.

[Analog Kid]

And who is "MrAI"?

[KE5FX]

The object of MrFusion's sibling rivalry?

[G0HZU]

If it helps demonstrate the power of using degeneration up at RF, have a look at one of my old reference LNA designs below. This is a low noise BJT RF amplifier that uses inductive degeneration at the emitter and some collector-base degeneration (negative feedback) to achieve a good compromise between noise figure and input and output match from 1 MHz to just over 100 MHz. This produces a flat gain of just over 15dB and a low noise figure and good port VSWR.

This is one of the reference amplifiers I use to do sanity checks on my noise figure measuring gear. Because the input and output VSWR is very low, it produces low uncertainty. The noise figure is a flat 1.3dB all the way up to 100 MHz.

Note that this is the original design simulation. The real version of the amplifier isn't quite this good. The noise figure of the real amplifier is just under 1.4dB most times I measure it and the input and output VSWR is about the same up to about 100 MHz. I can improve on the noise figure and the VSWR but this comes at the expense of bandwidth. So this design is fairly optimal up to just over 100 MHz.

The degeneration helps produce consistent performance all the way up to about 100 MHz or so.

It's a great way to make sure my noise figure meter is working correctly when measuring noise figures from a few MHz up to about 145 MHz.

[KE5FX]

Nice.  Have you posted a schematic of that one? 

[G0HZU]

Nice.  Have you posted a schematic of that one?

Not yet. I'll dig out the real amplifier over the weekend and demo it on a VNA and a noise figure meter. It uses a classic 2SC3355 BJT from NEC and this BJT was very special in its day. In this application it only draws about 6mA so the large signal handling is very poor. Therefore, this amplifier isn't of much use outside its intended use as a reference amplifier for my noise figure system.

There's nothing special or clever in the design, it just uses C-B resistive feedback and a small amount of emitter degeneration using inductance. This is achieved by not having the shortest possible emitter leg connection. So the original leg of the BJT can provide the degeneration here.

[KE5FX]

There's nothing special or clever in the design, it just uses C-B resistive feedback and a small amount of emitter degeneration using inductance. This is achieved by not having the shortest possible emitter leg connection. So the original leg of the BJT can provide the degeneration here.

Makes sense.  It might be interesting to try duplicating it to see how it looks on my 8970B, if you do get a chance to document it.  Most HF noise figure measurements I've made on that box have come out a bit worse than expected, and that might be a good excuse to look into it further.

[MrAl]

And who is "MrAI"?

Ha ha, that's what I was wondering too

I got my name from a nice older Spanish lady who used to call me (in all caps) MR AL.  She was really cool.  Long time ago.

[G0HZU]

Here's a VNA plot showing S21 S11 S12 S22 for the BJT amplifier with degeneration. I've also measured the noise figure using a 346A noise source and a E4440A PSA spectrum analyser.

I used an N4431-600006 B Ecal to calibrate the VNA.

You can see that the noise figure isn't quite as good as the simulation but it is typically just under 1.4dB according to the analyser.

The return loss of port 1 and port 2 of the amplifier is > 30dB up to about 100 MHz. The aim here was to make the port match as good as possible whilst still achieving a low noise figure. It is possible to get the noise figure lower than this by changing the degeneration and the bias point. But when I did this the amplifier lost some bandwidth.