@ Bob Cordell
Hi, you asked me to post my idea, & i did in Post # 6229, but you havn't replied ?
Maybe you misunderstood what i meant about the IR Element for detection ? I wasn't talking about using an IR detector as mentioned, off the shelf & using it's alarm etc output 😀
Rather just using the Actual IR element itself, combined with a voltage comparator/threshold/triggering etc type of circuit, which then feeds the bias etc, to control it.
Hi, you asked me to post my idea, & i did in Post # 6229, but you havn't replied ?
Maybe you misunderstood what i meant about the IR Element for detection ? I wasn't talking about using an IR detector as mentioned, off the shelf & using it's alarm etc output 😀
Rather just using the Actual IR element itself, combined with a voltage comparator/threshold/triggering etc type of circuit, which then feeds the bias etc, to control it.
Yeah, and also widespread industry defintions may not be optimal for discussing audio amplifiers. And if that's a problem, maybe we should just make up all our own bias terms altogether, rather than using the standard words but with different definitions.
Hi Zero D,
Sorry to be late in responding. I guess the sensor would be mounted somewhere a bit away from one of the black plastic output devices and look at it. I guess the advantage that you see is the lack of thermal inertia or load by using infra-red. I think the approach likely would add too much cost.
Perhaps more importantly, I think the problem is that we are not trying to measure the temperature itself, as we would if we wanted an over-temperature alarm or we wanted to control the device temperature, but rather we want something that will track the temperature in such a way as to keep the voltage across RE at about 26mV.
This is not an idea that I would pursue.
Cheers,
Bob
@ Bob Cordell
Yes the sensor would be mounted away from one of the black plastic output devices and look at it.
Well i think it might be possible to combine this temp tracking idea, with my other idea, which was to monitor Re for 26mV etc & compare this to a 26mV etc reference, & a circuit to auto adjust & maintain 26mV etc.
Yes the sensor would be mounted away from one of the black plastic output devices and look at it.
Well i think it might be possible to combine this temp tracking idea, with my other idea, which was to monitor Re for 26mV etc & compare this to a 26mV etc reference, & a circuit to auto adjust & maintain 26mV etc.
Yes, that would be perfect. You really need special words and names for this specialty field. Don't confuse others by using the same general name but meaning different things.
I am loud mouth about this because it did wasted my time as I was confused by it. Call it however which name, don't confuse people by calling Class B.
Does it really matter? If you set out to make a class B amp and the conduction angle is 180.1, I would call it Class B.
THx-RNMarsh
+1
Even if I ignore the industry standard definition of Classes for ALL amps, just look at Self's invented definition of Class B in page 82
"My definition of Class-B is that unique amount of bias voltage which causes the conduction of the two output devices to overlap with the greatest smoothness and so generate the minimum possible amount of crossover distortion."
Even at this, the bias voltage for BJT and MOSFET are different. Their phase angle or % are different. How does that make it clearer?
AND remember, again, and I cannot stress enough, Classes of amplifiers in the industry are defined for ALL amplifiers, not just push pull amplifier with two complementary devices. There is no crossover distortion for a single common base/gate or common emitter/source amplifiers that enjoy wide spread use. They can be designed as Class A, B or C easily. Calling it a class B just in the view of a push pull is causing much more confusion than clearing up anything.
I think Self explanation / example is fine - you can never hit exactly conduction angle of 180.00.
But in practical speaking, is it okay to call most commercial amplifiers Class AB?
Some manufactures also using "High Bias" so amplifier running in Class A with low volume and the entering "Class AB"
Thinking of crossover distortion, why aren´t so many manufactures using "Error correction" in amplifiers today?
(It seems from reading a lot of Service manuals, that many using a standard EF3 outputstage")
What "Class" can we define Member "OS" Slewmaster EF OPS?
anyone found a "optimal bias" settings for Slewmaster board?
Again, you are thinking the definition in audio amplifier only. How about all the different amplifiers in electronics. This audio push pull amplifiers is only a very small facet of amplifiers. You think it make sense to make this tiny facet of audio amplifier as the center by which everyone else has to follow?
Forget the 180 deg, 181 deg or 179 deg.
By whom?
😕😕 You’ve been repeatedly saying that classes A, AB, B and C are “defined” but now with your above statement you have me really confused. Please could you clarify exactly what you think the definitions are? And I’m not being facetious; this is a genuine query.
Really, In my book it's very simple, Class A is when both transistors in a pair simultaneously are delivering current to the load, the Class B transition is when you run out of bias and one of the transistors in the pair stop delivering current to the load.
I think about all amplifiers (for Hifi) sold today have biasing of the output pairs, thus they are all class AB. (class D and variants omitted)
I think about all amplifiers (for Hifi) sold today have biasing of the output pairs, thus they are all class AB. (class D and variants omitted)
This is impossible. One device sources current and the other sinks current. They cannot both deliver to the load, as the load current can only be in one direction at once.
Did you read my response to you? there are many other amplifiers not in push pull, that does not have crossover distortion. The industry Classes are for ALL amplifiers, not this small facet of audio amplifiers.
Read the standard Classes definitions.
Even limited to audio amp, it is written and agreed that transistors do not have a clean cut off, you cannot define 180 or 181. The cross over spread out in a few degrees.
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Yes
Where are these “standard class definitions”? By whom are they defined and why are you refusing to state what you think they are?
No, you should know what is the standard definition of Class A is 360, Class AB is between 360 to close to 180, Class B is 180 and Class C is less than 180.
You and Self is trying to redefine a class only at the narrow point of view of audio push pull amplifier. There are other amplifiers that is not push pull and no cross over distortion. audio amp is not the center of electronic amplifiers.
You bog up in thinking this is amplifier of all amplifiers.
Please explain yourself.
Not really. And I thought it was clear I don’t go along with Self’s definition. I’m just pointing out that the “standard” definition is flawed. How do you build a class-B amplifier, i.e. one with 180 degree conduction? At what point does it become class-C? 179.999? 179.9? 179.8? 179? At what point does it become class-AB? 180.001? 180.1? 181?
Real Class A can only exist in single transistor🙂
Others are push pull with high bias.
Or Class AB
Class B is only theoretical🙂
Others are push pull with high bias.
Or Class AB
Class B is only theoretical🙂
In which case, the majority of class A power amps would have to be renamed to class AB.
(most serial manufacturers have been using the definition of class A as idle dissipation equal to max output power in 8 ohm)