Yes I understand, I was trying to see which method had an advantage over the other. Can't see it at the moment except the point Stuart made about the accuracy.
Also, JC stated that with separate servo's at each output you would lose the differential correction which I don't see either; if both outputs are controlled to ground, the differential offset is automatically controlled to zero.
jd
No, but you said:
... which is not correct. When you are comparing (nulling) both outputs to ground, you are also ensuring that they are equal, ie no differential offset between the outputs.
jd
This is a situation where actual operation is very useful, like in a lab. If you remove one servo, the output will change in one way. If you change to the other servo and remove it instead, you see a different output change, or error. One is called a common mode error, the other is called a differential mode error. They are different in character, but they are both errors.
Only for the reason that 15mA is very high for a BL so very few would land
in that zone and V's are very hard to find - for us mere mortals
Having said that, I think 10mA BL's are fine - you will find the IP device
transfer curve is the least of your worries in the Blowtorch design. Other
non linearities will take precedence over the difference between a few mA
Idss IP devices, obviously provided they are all matched.
T
But linearity of transfer characteristics is much better near to Idss. And even for FB designs there are no stability issues - depends on overall design. If you compare high and low idle, you get both lower distortion and better sound
You're right PMA, I forgot this is the venue for open-loop hand sorted design.
Look everyone, I had to 'cherry-pick' from 100's of devices to get the high Idss parts that make it easiest to get lowest distortion, with low Cin, and highest peak output current.
You can approximate it with paralleling input devices, but then you will have twice the input capacitance, and you had better not use more than a 10K input pot, or you will have a lot of extra distortion.
You can approximate it with paralleling input devices, but then you will have twice the input capacitance, and you had better not use more than a 10K input pot, or you will have a lot of extra distortion.
That's it, definitely. Or just sorted.
Also, the high idle is difficult in the monolithic ICs. I assume we have collected enough good reasons why to go discrete.
You might just as well select for Cin and assume that IDss does not change.
For me, it appears quite shortsighted to think that one gets the same input capacitance
for average and extreme IDss&gm devices made on the same process.
I'd bet there is a correlation. I'll check this next week with BF862 if I have left enough of them.
Gerhard
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Well, that brings up my (somewhat naive) question- John says that paralleling two lower Idss devices doubles the input capacitance. I can see that it's double the input capacitance of one lower-Idss device, but in circuit, will the input capacitance be double that of a single device with twice the Idss?
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