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Old 23rd August 2012, 12:02 AM   #31
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Quote:
Originally Posted by RNMarsh View Post
PS Waveb --- that is NOT discrete circuitry. We mean no IC's. As in -- make an opamp without the IC. Then it would be compared to IC form. A version of the AD627 with individual parts - no IC's.
I am sick of designing discrete opamps in late 70'th when I believed that it is the building block of the future that outperformed everything else, including tubes. I was young and hot then.

Ok, let it be not discrete, let it be hybrid. But what the point of using discrete transistors when using a couple of chips and few resistors outperform?
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Old 23rd August 2012, 12:07 AM   #32
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Originally Posted by Wavebourn View Post
I am sick of designing discrete opamps in late 70'th when I believed that it is the building block of the future that outperformed everything else, including tubes. I was young and hot then.

Ok, let it be not discrete, let it be hybrid. But what the point of using discrete transistors when using a couple of chips and few resistors outperform?
Then there's no point to this exercise I guess?

An LME49710 + LME49600 will drive most anything really.
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Old 23rd August 2012, 12:11 AM   #33
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Originally Posted by dirkwright View Post
Then there's no point to this exercise I guess?

An LME49710 + LME49600 will drive most anything really.
Exactly! Make from them a classical instrumentational amplifier with gain like 70 dB flat beyond audio frequency band and no need for discrete components. Well, to increase PSRR I would probably add voltage stabilizer for the dual input chip, powering the output chip from higher voltages to get better headroom.
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Old 23rd August 2012, 12:18 AM   #34
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Originally Posted by dimitri View Post
Richard, AD627 is micropower opamp. Do you mean ADA4627, the substitute for OPA627?
I suspect Scott has the OPA627 in mind: http://www.ti.com/lit/ds/symlink/opa627.pdf
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Old 23rd August 2012, 12:19 AM   #35
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I didn't think it was possible, but if you're not counting current sources, this one has 8 transistors and 1 current source. It doesn't meet the output offset requirement. Oh, and this is at 2+ Vrms output. So, distortion is lower at 1 Vrms.
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Last edited by dirkwright; 23rd August 2012 at 12:27 AM.
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Old 23rd August 2012, 12:20 AM   #36
bcarso is offline bcarso  United States
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And that (OPA627) shouldn't be too hard to beat. I forget what Groner found they did at a high noise gain.

To begin with, they use P channel FETs in the input.
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Old 23rd August 2012, 12:29 AM   #37
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FFT @ 1 Vrms or so into 30 ohms.
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Old 23rd August 2012, 12:36 AM   #38
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You guys are a riot. go back and read what Scott said he was interested in doing. What he proposed, pls.
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Old 23rd August 2012, 12:38 AM   #39
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You guys are a riot. go back and read what Scott said he was interested in doing. What he proposed, pls.
I didn't read that thread so I don't know.
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Old 23rd August 2012, 12:38 AM   #40
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Originally Posted by Wavebourn View Post
Exactly! Make from them a classical instrumentational amplifier with gain like 70 dB flat beyond audio frequency band and no need for discrete components. Well, to increase PSRR I would probably add voltage stabilizer for the dual input chip, powering the output chip from higher voltages to get better headroom.
Sorry, I am wrong. The point in exercises is building muscle masses and great shape of the body and excellent coordination between body and mind. And in knowing behavior and limits of the topology. Go for it!
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