janneman said:
Yes we can, but so can we choose to go for the ancient greek language and culture instead of e.g. french. It might be interesting and entertaining, but to expensive and ultimately useless for any practical purposes. Discretes are soon going to be only a die hard DIYer and simulation afficionados thing.
pioneer, denon, yamaha, harmon kardon, and others still use discretes. granted, some of them look like an amp design from the early 70's (resistors instead of current sources, no current mirrors, darlington output transistors) but discretes are still in use on a massive industrial scale. class D makes for nice "drop-in" amps, and many manufacturers are using large chip amps (STK430-xxx), but there are still plenty of discrete amps being rolled out every year.
Here is the link to bateman's capacitor articles:
http://uk.geocities.com/cyrilb2@btinternet.com/downloads_4.html
ZAP
john curl said:
Pease writes an article with references to the uA709 you ask about the LM725. You folks are going to have to let go of some of this 40yr old stuff and move forward. Paul Brokaw and Mitch Madique presented cross quaded input devices and outputs on a thermal center line with NO thermal feedback (fractional ppm) more than thirty years ago, it was then end of story.
Sorry for my lack of precision.
A high precision monolithic super-beta operational amplifier
Maidique, M.A.
Solid-State Circuits, IEEE Journal of
Volume 7, Issue 6, Dec 1972 Page(s): 480 - 487
Summary: A single-chip (67/spl times/90 mil) integrated-circuit operational amplifier using thin-film resistors and super-gain transistors has been designed to achieve dc follower accuracies of 0.001 percent with 100-k/spl Omega/ source resistance. The circuit achieves gains of 140 dB using thermally balanced layout designs for both input and output stages, nulled drifts of 0.3 /spl mu/V//spl deg/C, and offset currents well under 1 nA. All other dc specifications including power-supply variation error (PSRR), common-mode gain error (CMRR), etc., are in the 1-10 ppm error range; and a procedure is given by which long-term drifts of less than 10 /spl mu/V/month can be assured. AC performance is comparable to general-purpose integrated-circuit operational amplifiers, i.e., f/SUB t/=300 kHz and slew rate of 1.2 V//spl mu/s at gain of ten. The circuit is externally compensated for unity gain with a single 390-pF capacitor and is fully input and output protected
EDIT - Excuse the special character snafus, but the abstract gets across the point Solomon pointed out a problem, it was easily solved, end of story.
A high precision monolithic super-beta operational amplifier
Maidique, M.A.
Solid-State Circuits, IEEE Journal of
Volume 7, Issue 6, Dec 1972 Page(s): 480 - 487
Summary: A single-chip (67/spl times/90 mil) integrated-circuit operational amplifier using thin-film resistors and super-gain transistors has been designed to achieve dc follower accuracies of 0.001 percent with 100-k/spl Omega/ source resistance. The circuit achieves gains of 140 dB using thermally balanced layout designs for both input and output stages, nulled drifts of 0.3 /spl mu/V//spl deg/C, and offset currents well under 1 nA. All other dc specifications including power-supply variation error (PSRR), common-mode gain error (CMRR), etc., are in the 1-10 ppm error range; and a procedure is given by which long-term drifts of less than 10 /spl mu/V/month can be assured. AC performance is comparable to general-purpose integrated-circuit operational amplifiers, i.e., f/SUB t/=300 kHz and slew rate of 1.2 V//spl mu/s at gain of ten. The circuit is externally compensated for unity gain with a single 390-pF capacitor and is fully input and output protected
EDIT - Excuse the special character snafus, but the abstract gets across the point Solomon pointed out a problem, it was easily solved, end of story.
One of the opamps on my prototyping board -- the LT1013 of which I have like popcorn, and the LM4562 -- both with a 1K load.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Re: Re: better op amps in better topologies
My recollection is that Bateman used a "active feedback" Reddy style composite amplifier in his oscillator, these are entirely dependant on op amp matching for any improvement - I think Soliman had articles on active op amp compensation in Wireless World in the 80's
the topology can work to some degree as Bateman shows, more ususally this topology is chosen for reduced phase errors in active filters
I'd claim using "active compensation" topologies for output load distortion reduction is less reliable - for best results you'd have to be sure that you loaded the feedback path op amp exactly the same as the forward path op amp
op amp parameter matching in these circuits usally is assummed when using dual op amps, but finding data on the degree of parameter matching of the 2 op amps in a monolithic dual is rare
for more fun you could try to predict thermal crosstalk effects when using both sides of a dual in a single loop
Jung style multiloops should give more robust reduction of output loading distortion reduction
as I mentioned in my thread on composite op amp circuits I've built high loop gain multiloop circuits and couldn't see 1 KHz 2nd order IMD product in a setup with ~ -160 dB resolution limit
myhrrhleine said:
zapnspark said:
My recollection is that Bateman used a "active feedback" Reddy style composite amplifier in his oscillator, these are entirely dependant on op amp matching for any improvement - I think Soliman had articles on active op amp compensation in Wireless World in the 80's
the topology can work to some degree as Bateman shows, more ususally this topology is chosen for reduced phase errors in active filters
I'd claim using "active compensation" topologies for output load distortion reduction is less reliable - for best results you'd have to be sure that you loaded the feedback path op amp exactly the same as the forward path op amp
op amp parameter matching in these circuits usally is assummed when using dual op amps, but finding data on the degree of parameter matching of the 2 op amps in a monolithic dual is rare
for more fun you could try to predict thermal crosstalk effects when using both sides of a dual in a single loop
Jung style multiloops should give more robust reduction of output loading distortion reduction
as I mentioned in my thread on composite op amp circuits I've built high loop gain multiloop circuits and couldn't see 1 KHz 2nd order IMD product in a setup with ~ -160 dB resolution limit
syn08 said:
Yes, though we had some pans in the fire at Micropower. I don't remember if Nova got seed money from ADI. My high school chemistry teacher's son was Nova's first "knob tweaker" in the fab (I found out years later that they were related).
Jackinnj - that second plot is what I expect these days.
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