High impedance vrs Low impedance.

[dragonbat13]

I have tried to wrap my head around impedance for a very long time it it just doesnt sink in. And I know it will all come together with one detail that apparently am missing.

Ok, this is the way I see it so far. You put a lot of voltage on the high impedance side with low current, and the low impedance side will build high current at a low voltage. RIGHT? Isn't this how an output tranny works from what I understand.

But then when I read about circuits the impedeances always seem to be backwards.

I would greatly appreciate anybody helping with this.

There is one simple thing I am not getting and I know it's right in front of me.

[luix]

But then when I read about circuits the impedeances always seem to be backwards.

Sorry, I can't understand this sentence, can you be more specific?

[dragonbat13]

It seems as if the impedance are designed to loos power instead of building power.

[luix]

It seems as if the impedance are designed to loos power instead of building power.

Just to point out, power can be generated, transferred, dissipated but not builded

The amplification of an audio frequency signal can be divided in two main branch:
1) Level amplification: the voltage of the signal is magnified, it's also possible to amplify the current but usually we amplify voltage... long story.
2) power amplification: the power of the signal is magnified.

For level amplification is better to have a low impedance driving an high impedance, because the voltage divider formed by the internal resistance (or impedance) and the load resistance (impedance) have minimal effect.

VoltageAmp.png

For example an internal resistance of 100ohm loaded by a resistance of 100kohm will give a gain of 0.999 that is approximable to 1, so no attenuation.

For power amplification you should consider the maximum power transfer to the load and in this case the two impedance should be matched, so an amplifier with an internal resistance of 100 ohm can deliver the maximum power to a 100 ohm load.

Hope this will help your "spaghetti" thoughts on impedance

[pdf64]

...But then when I read about circuits the impedeances always seem to be backwards...

Without an example of what you're getting stuck on, it's not really feasible to attempt help.

...For power amplification you should consider the maximum power transfer to the load and in this case the two impedance should be matched, so an amplifier with an internal resistance of 100 ohm can deliver the maximum power to a 100 ohm load...

The max power transfer theorem makes for very inefficient systems, hence it (and its associated 'impedance matching' arrangements) finds little application outside of RF / transmission lines. Would you really want the the voltage to your house lights to halve when you turn your oven on? We're warming the planet enough as it is, without designing things to intentionally waste half the electricity generated.
Hence impedance bridging type arrangements, having much greater efficiency, are ubiquitous.
However, pentode power amps have rather high (open loop) output impedance, typically at least several times that of their intended load impedance. The point of the OT is to 'match' the speaker impedance to that of the intended loadline; pentode plate impedance is typically somewhat higher than that of the chosen loadline.
Typical solid state amps have a very low output impedance, though they (almost) invariably require negative feedback to stabilise their operating point, so it's not really an apples to apples comparison.

[luix]

...For power amplification you should consider the maximum power transfer to the load and in this case the two impedance should be matched, so an amplifier with an internal resistance of 100 ohm can deliver the maximum power to a 100 ohm load...

The max power transfer theorem makes for very inefficient systems, hence it (and its associated 'impedance matching' arrangements) finds little application outside of RF / transmission lines. Would you really want the the voltage to your house lights to halve when you turn your oven on? We're warming the planet enough as it is, without designing things to intentionally waste half the electricity generated.

AHahaha! You're right, my mistake, the theorem is useful for RF, sorry but lockdown is hazing my mind.

Of course the less is the source impedance compared to the load, the less power is dissipated on it ad so it's transferred to the load.

[dragonbat13]

The detail I was missing was the fact that AC currents are sine waves, and DC currents are not. Resistance only effects DC voltage (and in effect current) where Impedance reduces amplitude in AC current. Or something close to that. This makes some sense to me. I need to freshen up my load line knowledge and such through Merlin's book. But for the most part I somewhat understand the two terms from a basic electronics site I found.

https://www.electronics-tutorials.ws/ac ... -html.html

[blackeye]

Resistance only effects DC voltage (and in effect current) where Impedance reduces amplitude in AC current.

You are getting closer.

First consider that Impedance = Resistance + Reactance.

Resistance will resist DC and AC current alike. It doesn’t care how the current is changing. We can consider resistance the same for all frequencies of current. (Remember DC can be thought of as AC with a frequency of 0Hz.)

Reactance does care how the current is changing so its resistance to a current depends on frequency. Capacitors and inductors are the two primary examples of where reactance comes into play.

Impedance is just the sum of these two components. Many times in circuit analysis the reactance is sufficiently low at the frequencies we are interested in. In this case, we can ignore reactance and simply use resistance and impedance interchangeably.

Hopefully I’ve said it well enough to be correct and understood. Good luck in your journey, we are all still learning.

[dragonbat13]

Yes, that summed it up. Thanks.

[Colossal]

I like to think of impedance as frequency dependent resistance.

[didit]

You are getting closer.

First consider that Impedance = Resistance + Reactance.

All seems rather dynamically imaginary to me.

Best .. Ian