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- Thread starter flg
- Start date

Not inverting if you hook it up as laid out....

ehh, because input ground resistor connects to -out, I guess

but with +out connected to ground/chassis, strange thing

ehh, input cap C3 is also a polar electrolytic cap

well, it is according to parts number

It's a

lot of film caps.

And you can't get a tube or a transistor to give you voltage gain and

not have inversion somewhere unless you introduce the dreaded

transformer. Non-inverting amplifiers with voltage gain simply find

some way to flip the phase an even number of times. In this amp,

the second time is at the output terminals.

Doh!

its ok, noones perfect

I suppose using matched outputs are more or less standard now ?

The mu follower has a relatively high DC impedance, but it is an active

component with an AC negative resistance. It contributes to raising the

apparent output impedance of the amplifier.

I am confused by these statements

If it is "an active component with an AC negative resistance" how can it's contibution be higher impeadance? It's negative, simply speaking, thats lower.

It's aelectrolytic. Measures and sounds better than asilk

lot of film caps.

And you can't get a tube or a transistor to give you voltage gain and

not have inversion somewhere unless you introduce the dreaded

transformer. Non-inverting amplifiers with voltage gain simply find

some way to flip the phase an even number of times. In this amp,

the second time is at the output terminals.

If it is "an active component with an AC negative resistance" how can it's contibution be higher impeadance? It's negative, simply speaking, thats lower.

Of additional interest is an answer/explanation for the amplifier without loop feedback, driven by one complete sinusoidal signal into a load of 8 Ohms. What is its output impedance it experiences along the signal trajectory? Is is a constant 10 Ohms like in the quiescent mode?

If it is "an active component with an AC negative resistance" how can it's contibution be higher impeadance? It's negative, simply speaking, thats lower.

Silk

You should have been into capacitor designing, instead of tanning leather strings.

We have 2 sources of gain totalling 29db loaded with 8 ohms. We have at this point neglected the Drain impeadance and the Mu follower contibution to the impeadance the drain see's. And the feedback....But it's more complicated than that. The Mu follower current source on

top of the circuit also contributes to gain, adding maybe 5 dB. So now we estimate that with infinite Drain resistance the gain is 29 dB, which is

28X.

OK so far?

So the impeadance value of the Mu follower can be calculated to exhibit 10 ohms of paralell load to the 8 ohms?But we actually experience 23 dB gain due to the finite Drain resistance(s) and the contribution of the DC feedback loop. This 5 dB drop is a factor of 0.56X, and is equivalent to our high Drain resistance example driving 8 X 0.56, which is 4.5 ohms

So now we have an apparent Drain resistance which is equivalent to that value which paralleled with 8 ohms gives us 4.5 ohms. That resistor is close to 10 ohms.

Wait a minute, The -5db that reduced our theoritical gain from 29-23 included feedback and Drain resistance(s) and was used to determine the actual Drain load was 10 ohms?Without the R12/R11 loop, the output impedance of the amplifier is 10

ohms...

I'm missing something here. There are a few to many "DC"s and "Drain"s maybe?

This seems similar to the way you figure output Z across the load range in a power supply?

Thanks for making the connection to my previous employer Rohm and Haas. This pair of entreupreuners started selling chemicals to the leather industry in 1907. I am still chasing new tanning agents. Collagen [skin fiber] is a poor eco-dielectric. It has the dreaded zwitter ions which ironically are needed for tanning. Amine groups for aldehyde and carboxylic for chrome tannages. I may be able to get the dielectric properties of silk [or better] with leather as we know it. Food for my thought.You should have been into capacitor designing, instead of tanning leather strings.

So the impeadance value of the Mu follower can be calculated to exhibit 10 ohms of paralell load to the 8 ohms?

The open loop output impedance is a function of the Drain resistance of the

gain Mosfet, the output resistance of the Mu follower, and the DC feedback

loop circuit. Taken together, the value is 10 ohms. as calculated by the

measured open loop gain into 8 ohms vs the expected open loop gain.

I must admit to not understanding how to derive many of the numbers being tossed around.

The important thing is to be able to visualize the concepts. If you want

really accurate information, build the thing and measure it.

Regarding R085 Drain impeadance, in one post N.P. says its lower than the R100 but the Sony Sit is much lower??? he also mentions it is dependant on your op point, but, the op point we're looking at is almost the same?