Products > Test Equipment
Test Equipment Anonymous (TEA) group therapy thread
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.
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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 :)
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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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