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Old 19th July 2013, 11:07 PM   #21
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Quote:
Originally Posted by buzzforb View Post
Here is an idea. Little unsure if it will work as setting gain is in question.
xconductance of gain device through closing resistors

there is also issue of output offset , output impedance ( roughly closing resistors value , if going low) etc.

thought , nice playground for next few months

addendum - developing ZM's I/V conversion stage for DAC resulted in having dual servos for input and dual servos for output

simple for no active voltage gain stage
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Old 19th July 2013, 11:14 PM   #22
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Gotcha. Thanks. It appears adding a stage will be beneficial in more ways than one. Servos scare me
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Old 19th July 2013, 11:18 PM   #23
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not just you

old ookers (geezers) made nuclear science of them , just to scare greedy boyz and increase their own price on market

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Old 19th July 2013, 11:22 PM   #24
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I get the basic concept but font think it is basic in this situation. Gotta start digging. Looking forward to my fair lady. Got some 6v6's that are lonely.
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Old 19th July 2013, 11:25 PM   #25
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no 6V6

not enough xconductance

made for quayzee ones , in range of 7788 or 6688 triode , EC8010 , 6Н6П ,6Н30П, 6Н23П , 6DJ8 .......... all of them being on wakoo wild side of toobs
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Old 19th July 2013, 11:29 PM   #26
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Crud.

On nother topic...or orignal one. Opa uses servo fed back to current mirror gate, but this is dealing wit common mode voltage, which I know nothing about. In order to influence ouput, I would need servo to influence cs of LTP or current mirror correct.
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Old 20th July 2013, 12:07 AM   #27
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Default ?

What about this
Attached Images
File Type: png huh.png (31.7 KB, 136 views)
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Old 20th July 2013, 04:37 AM   #28
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1.dots are important in schematic
2.that servo is same as you are lifting your self , pulling neck-tie with hand
3.
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Old 20th July 2013, 12:32 PM   #29
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http://ee.sharif.edu/~elec3/06_advanced_opamps.pdf
Found a good article.
IN order to have sufficient drive capability, It seems I would have to do one of the following
1. parallel input pairs to increase gain
2. another stage for increased gain and drive capability
3. output buffer for better drive capability

Looks like the latter two allow fro dropping of servo if done properly, but could be wrong.
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Old 20th July 2013, 01:03 PM   #30
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ZM,
What is your comment on the whole bit about it wanting a capacitive load. The Bartola article doesnt seem to mention it as an issue. We could raise the gain of the FE by loadng it with a CCS, but that would also raise Zo, correct. I also like the idea of a resistive load, but understand the benefits off the CCS.
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