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| Test Equipment Anonymous (TEA) group therapy thread |
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| Vince:
--- Quote from: ch_scr on July 05, 2022, 07:13:56 am --- --- Quote from: Vince on July 04, 2022, 11:52:47 pm --- So wow... can't believe it, this 2525 is a RACE CAR !!!! 120V/µs 20MHz ?!! :wtf: Wow, 120V.... so far all the op-amps I garnered were at best 20V for the TL054.. and have some that do LESS than one volt IIRC ! :scared: Can't help, I now feel the urge to wire them up and see that slew rate for myself ! Datasheet specifies what parameters to use to have a chance of getting that... --- End quote --- Vince beware! These are uncompensated amplifiers. Which means they are fast, damn fast! But this also means they will oscillate below a certain amplification, usually 5 or so. Have a close look at the datasheet. [..] --- End quote --- Yeah no worries, the datasheet is upfront about that. At the top f the front page they say : These dielectrically isolated amplifiers are controlled at closed loop gains greater than 3 without external compensation. and also : Compensation pin for unity gain capability So as BD said just put a cap on the compensation input. To decouple the power pins, the datasheet shows a 1nF cap in // with a 1uF for the negative rail, and for the positive rail 1nF cap in // with a 1F cap, which I assume is a typo ! :-DD That said, seeing the amp oscillate is interesting and educational in itself, then add a compensation cap, starting from a very low value, increasing it progressively to see how it affects the oscillation. Hiding the ugly stuff is bad, makes the student think / believe that IC's are magical things that "just work" and don't require you to think. ;D |
| tggzzz:
Three questions about the components below, on two different test equipment boards: * what's the "perforated tube" in the centre of both pictures? My guess is an inductor, but why that peculiar construction? * is there anything interestingly special about the reed relay, Electrol R4174-1 * how long would it take for a ferengi to spot the gold and other components? |
| Robert763:
--- Quote from: Vince on July 05, 2022, 10:27:34 am --- --- Quote from: McBryce on July 05, 2022, 08:13:12 am ---Why are you trying to do this on a phone at all?? I'm sure you have a PC with a speaker, microphone and internet connection. Click the link on a PC and you don't need the phone to be involved at all. For free, without having to register or give credit card details. McBryce. --- End quote --- No there are no mic or camera on my computer, otherwise I would as you say just use that, rather than trying to get it working on a bloody smartphone ! ;) It's a desktop computer not a modern laptop which have mic and camera as standard since these days laptops are basically closer to a glorified smartphone than an actual computer. --- End quote --- So go buy a USB camera / Mic or better a USB camera and standard headset with mic and off you go! |
| Robert763:
--- Quote from: tggzzz on July 05, 2022, 10:59:41 am ---Three questions about the components below, on two different test equipment boards: * what's the "perforated tube" in the centre of both pictures? My guess is an inductor, but why that peculiar construction? * is there anything interestingly special about the reed relay, Electrol R4174-1 * how long would it take for a ferengi to spot the gold and other components? --- End quote --- I think it is a delay line. It's construction is a bit like a non-inductive power resistor but it's clearly not a power circuit. |
| Vince:
--- Quote from: tggzzz on July 05, 2022, 09:58:04 am --- --- Quote from: Vince on July 04, 2022, 11:52:47 pm ---So wow... can't believe it, this 2525 is a RACE CAR !!!! 120V/µs 20MHz ?!! :wtf: --- End quote --- And then you look at the slew rates of earlier current feedback opamps :) Or modern opamps that have to be capable of driving modern ADCs/DACs :) --- End quote --- No, sounds to me like you are comparing apples to bananas, that's naughty. This 2525 looks like, still, a fairly conventional / general purpose op-amp, so you need to compare it other mainstream op-amps of the era. So I am looking at the datasheet of old op-amps I have in my stock, let's see... have 358 and LM4250. Slew rate is so spectacular that tehy don't even specify it ?! :wtf: I guess that means ; " If you care about slew rate, this isn't the right part for you Sir.... ". Then I looked at the 741 so a bit more recent... and it's given at 0.5V/µs ................. |
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