By far my favorite attractions in Paris are the Panthéon, The National Museum Of Eugéne Delacroix, The Salvador Dali Exhibition and, of course, Versailles.
Can't wait for the next opportunity, I know a small hotel in Le Quartier Latin across Notre-Dame that is clean and not extremely expensive as one would expect in that area.
No hate mail from me, but IMO this is not "restating" but "reinventing". Why would anyone need to "reinvent" anything when it comes to the four feedback topologies is one of those impenetrable mysteries of life 😀.
That would be a good thing; unfortunately I don’t see how these new definitions would be equivalent with what Black taught us, a very long time ago. Hence the “reinvention” as a useless exercise 😀.
The next step would be to put these two set of definitions (Black and Bonsai) on two columns and show how they map, but I’ll stop short of asking for this, I’m not that of a cynical SOB 😀.
Another form to say what I said above. And combination(s) of them.
Surely my English is not too good.
Osvaldo, your English is fine. And your statements were correct. The sad thing is that you didn't read the thread, just jumped in and now you are repeating almost exactly what the discussion has been....
Jan
Jan
Let’s approach the subject of this thread a little differently. Around feedback loops, there are both voltage and current gains. One way to evaluate them starts with inserting a signal into the loop without disturbing impedances or component biasing. If two specific signals traveling in the forward direction around the loop (one immediately after the insertion point and the other immediately prior to it) are non-zero, then the signal gain and feedback are finite and non-zero. The following text and accompanying schematic provide a general example which supports and elucidates these claims.
Consider any amplifier that has inverting and non-inverting inputs and a single ended output. There is an impedance rd between the inputs. We could describe the output stage as a voltage source vo in series with ro or equivalently, a current source io in parallel with ro. And we could state that vo is equal to the unitless parameter A times the difference between the input voltages, or alternatively that vo is equal to the product of an impedance Z and the current flowing into an input, where Z = A · rd.
Let’s work with the first of each option pair. From the perspective of the inverting input, the combination of the output stage and feedback network looks like an impedance zf in series with a voltage source equal to vo times an attenuation factor β. Analysis of the accompanying circuit loop gives us:
There is less current than voltage gain when zf/rd is greater than one, but more when that ratio is less than one. The gains are equal when zf equals rd.
The situation is the opposite for feedback. Decreasing values of zf/rd lead to growing amounts of voltage feedback, an intuitively satisfying result. But increasing values of zf/rd mean that a smaller portion of ir is leading to a larger portion of if - that is, current feedback is rising.
The application of the forgoing analysis to the main subject of this thread should be clear.
Consider any amplifier that has inverting and non-inverting inputs and a single ended output. There is an impedance rd between the inputs. We could describe the output stage as a voltage source vo in series with ro or equivalently, a current source io in parallel with ro. And we could state that vo is equal to the unitless parameter A times the difference between the input voltages, or alternatively that vo is equal to the product of an impedance Z and the current flowing into an input, where Z = A · rd.
Let’s work with the first of each option pair. From the perspective of the inverting input, the combination of the output stage and feedback network looks like an impedance zf in series with a voltage source equal to vo times an attenuation factor β. Analysis of the accompanying circuit loop gives us:
a current gain of ir/if = (β·A+1) · rd/zf
a voltage gain of vr/vf = zf/rd + β·A.
a voltage gain of vr/vf = zf/rd + β·A.
There is less current than voltage gain when zf/rd is greater than one, but more when that ratio is less than one. The gains are equal when zf equals rd.
The situation is the opposite for feedback. Decreasing values of zf/rd lead to growing amounts of voltage feedback, an intuitively satisfying result. But increasing values of zf/rd mean that a smaller portion of ir is leading to a larger portion of if - that is, current feedback is rising.
The application of the forgoing analysis to the main subject of this thread should be clear.
Attachments
Well, just in case it was only mostly dead and not all dead. It's always good to be careful.
I'm just listening to genesis through a CFA.
And bathing in the light of a LED (quantum well).
Both debated technologies perform well , We can continue to debate them.
As a "pitchfork villager" , it is magic.
CFA controversy even triggered magic VAS's to accommodate magic
slewrates.
The semantics are positive ., may the arguments continue. 😛
OS
And bathing in the light of a LED (quantum well).
Both debated technologies perform well , We can continue to debate them.
As a "pitchfork villager" , it is magic.
CFA controversy even triggered magic VAS's to accommodate magic
slewrates.
The semantics are positive ., may the arguments continue. 😛
OS
To hell with popcorn the mouth to mouth stuff. Someone please smash the defibrillator with an axe.
(Moo Koo I know you are lurking. Do not send any more emails. You are under surveillance. Be warned!)
😀
(Moo Koo I know you are lurking. Do not send any more emails. You are under surveillance. Be warned!)
😀
OK, let's have a conversation. I answer your question, and you respond to Post 2548.
In common base mode, the base is at AC ground potential, if not DC ground potential. Since this is generally not the case with CFAs, no, I wouldn't say that.
If you want to study the CFA inv input, you should set all other independent sources to zero. Superposition principle. Therefor, from the point of view of the inv input, that transistor indeed works in common base.
Jan
Jan
I think seeing the CFA device(s) when the F of CFA is working, that means in a circuit in closed loop configuration otherwise letter F has no meaning here, as being in common base mode is fully misleading.
The CFA input stage is always described as a buffer (a voltage follower in series with a low impedance). It is sometimes said to be a kind of AC voltage regulator. The current it delivers is controlled by itself depending of its emitter load. In common base mode, the current is received, determined outside of the device.
Note that Cyril Mechkov complained about the lack of references to the devices mode in the litterature about CFA : What is the truth about the exotic current feedback amplifier? Is it something new or just well known old? Is it really a current feedback device?
But what was my surprise when browsing through reputable sources? I noticed that instead of being made related to the classical tricks widely used in transistor circuits, the current feedback amplifier is presented as something completely new. I have not met even a hint of the existence of such famous circuit ideas like "common-base" and "common-collector" configurations, "dynamic load", "bootstrapping", instead, I read direct statements like "the inverting input is its low-impedance output terminal"
Sorry, your reasoning is probably right but I do not see its aim.