>>Yup. Chopper, autozero, or other such schemes. They've been getting better at it--I remember the old ICL7650. It was pretty amazing in 1980, but you could practically draw sparks from the switching spikes. ;)>I think that was the amp that took seconds to recover from railing.Yup. The auto-zero just keeps on winding up.> >>>I saw the noise plot and wondered why it was only for a gain of 100. >>>Maybe birdies up at higher freq.? > >>That's my suspicion as well--either isolated switching harmonics or maybe an elevated noise floor if they're doing the spread spectrum thing. > >>What you usually have to watch out for is current spikes coming out the inputs--the bias current is far from constant, so chopamps are bad news when the source is high-impedance.>Input offsets tend to shift as a function of the capacitance that the >two inputs see. I'm optimistic that the ADA4522 is better.I'll be interested to hear more about it. Cheers Phil Hobbs
ADA4522 opamp hangup
Started by ●September 12, 2018
Reply by ●September 13, 20182018-09-13
Reply by ●September 13, 20182018-09-13
On Wed, 12 Sep 2018 17:53:50 -0700 (PDT), George Herold <gherold@teachspin.com> wrote:>On Wednesday, September 12, 2018 at 8:09:49 PM UTC-4, John Larkin wrote: >> On Wed, 12 Sep 2018 16:26:08 -0700 (PDT), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Wednesday, September 12, 2018 at 3:26:42 PM UTC-4, John Larkin wrote: >> >> On Wed, 12 Sep 2018 11:16:42 -0700 (PDT), George Herold >> >> <gherold@teachspin.com> wrote: >> >> >> >> >On Wednesday, September 12, 2018 at 11:45:38 AM UTC-4, John Larkin wrote: >> >> >> ADA4522 is an amazing amp. 55 volt supplies, low noise, 5 uV max >> >> >> offset, EMI hardened, pA bias current. But it has a hangup mode as a >> >> >> follower: if the output goes to V+ the input back-to-back diodes keep >> >> >> both inputs above the legal common-mode range. Pity it's not RRIO. >> >> >Huh that is a nice opamp. (Thanks, well slew rate not so snappy) >> >> >What do you mean by hangup? >> >> >Does it latch? Or take a long time to recover? >> >> > >> >> >George H. >> >> >> >> If the customer input is fairly high impedance, like 20K or so, and he >> >> briefly blips the voltage high, the input can hang high, even when the >> >> customer backs down. >> >> >> >> It just occurred to us that we could have that stage have a gain of >> >> +1.15 or something, which would keep the inverting input away from >> >> Vcc. That just needs two resistors and has no zener leakage concerns. >> >> We can cal around the gain. >> >OK, so a little gain kills it. If you didn't care too much >> >about the output impedance.. or you knew what it was driving, >> >you could throw away the gain on the output. >> >(but you know that...) >> >George H. >> >> I hadn't thought of that but you're right, the voltage at the >> inverting input has a gain of 1.000, after the divider. Unfortunately >> there is a load downstream. >> >> Hmmm, I think it works! The downstream load is about 5K, so we just >> add one 500 ohm resistor in series with the opamp output. >> >> https://www.dropbox.com/s/d7cpms6fcde6my2/ADA4522_fix.JPG?raw=1 >Huh, well that is not at all what I had in mind, but it >meets all the criteria.. constraining voltages. >with less parts and no matching. > >looks OK... even if the 5k ohm is not that firm. > >GH >(sometimes even the blind pig finds an acorn.)The cool thing about brainstorming, kicking problems around, is that ideas evolve and there is usually no one person to credit (or blame.) Most people are too insecure to play the game, especially online. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●September 13, 20182018-09-13
>The cool thing about brainstorming, kicking problems around, is that >ideas evolve and there is usually no one person to credit (or blame.)Brainstorming as originally defined has a bunch of rules that I can't even remember. Inventing stuff with a few smart people and a white board is the most fun you can have standing up. Part of what I do is to teach people the rhythm of doing that.>Most people are too insecure to play the game, especially online.Depends a lot on the environment. You need a reasonably thick skin unless you've been round long enough to know who you're dealing with. ;) Cheers Phil Hobbs
Reply by ●September 13, 20182018-09-13
On Thu, 13 Sep 2018 17:22:14 -0700 (PDT), pcdhobbs@gmail.com wrote:>>The cool thing about brainstorming, kicking problems around, is that >>ideas evolve and there is usually no one person to credit (or blame.) > >Brainstorming as originally defined has a bunch of rules that I can't even remember. Inventing stuff with a few smart people and a white board is the most fun you can have standing up. Part of what I do is to teach people the rhythm of doing that.It is great fun, and can be taught (mainly by example) but some people just can't do it. And there is sometimes the "out of the mouths of babes" effect, where an apparently unlikely person inspires something big.> >>Most people are too insecure to play the game, especially online. > >Depends a lot on the environment. You need a reasonably thick skin unless you've been round long enough to know who you're dealing with. ;)I can do it anywhere, but I have to be careful around customers. Some interpret brainstorming as uncertainty or incompetance; they want PowerPoints. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●September 13, 20182018-09-13
> can do it anywhere, but I have to be careful around customers. Some >interpret brainstorming as uncertainty or incompetance; they want >PowerPoints.I don't do PP--if people insist that means there's an irreconcilable impedance mismatch. Cheers Phil Hobbs (boarding doors just closed)
Reply by ●September 13, 20182018-09-13
On Thursday, September 13, 2018 at 3:34:07 PM UTC-4, John Larkin wrote:> On Wed, 12 Sep 2018 17:53:50 -0700 (PDT), George Herold > <gherold@teachspin.com> wrote: > > >On Wednesday, September 12, 2018 at 8:09:49 PM UTC-4, John Larkin wrote: > >> On Wed, 12 Sep 2018 16:26:08 -0700 (PDT), George Herold > >> <gherold@teachspin.com> wrote: > >> > >> >On Wednesday, September 12, 2018 at 3:26:42 PM UTC-4, John Larkin wrote: > >> >> On Wed, 12 Sep 2018 11:16:42 -0700 (PDT), George Herold > >> >> <gherold@teachspin.com> wrote: > >> >> > >> >> >On Wednesday, September 12, 2018 at 11:45:38 AM UTC-4, John Larkin wrote: > >> >> >> ADA4522 is an amazing amp. 55 volt supplies, low noise, 5 uV max > >> >> >> offset, EMI hardened, pA bias current. But it has a hangup mode as a > >> >> >> follower: if the output goes to V+ the input back-to-back diodes keep > >> >> >> both inputs above the legal common-mode range. Pity it's not RRIO. > >> >> >Huh that is a nice opamp. (Thanks, well slew rate not so snappy) > >> >> >What do you mean by hangup? > >> >> >Does it latch? Or take a long time to recover? > >> >> > > >> >> >George H. > >> >> > >> >> If the customer input is fairly high impedance, like 20K or so, and he > >> >> briefly blips the voltage high, the input can hang high, even when the > >> >> customer backs down. > >> >> > >> >> It just occurred to us that we could have that stage have a gain of > >> >> +1.15 or something, which would keep the inverting input away from > >> >> Vcc. That just needs two resistors and has no zener leakage concerns. > >> >> We can cal around the gain. > >> >OK, so a little gain kills it. If you didn't care too much > >> >about the output impedance.. or you knew what it was driving, > >> >you could throw away the gain on the output. > >> >(but you know that...) > >> >George H. > >> > >> I hadn't thought of that but you're right, the voltage at the > >> inverting input has a gain of 1.000, after the divider. Unfortunately > >> there is a load downstream. > >> > >> Hmmm, I think it works! The downstream load is about 5K, so we just > >> add one 500 ohm resistor in series with the opamp output. > >> > >> https://www.dropbox.com/s/d7cpms6fcde6my2/ADA4522_fix.JPG?raw=1 > >Huh, well that is not at all what I had in mind, but it > >meets all the criteria.. constraining voltages. > >with less parts and no matching. > > > >looks OK... even if the 5k ohm is not that firm. > > > >GH > >(sometimes even the blind pig finds an acorn.) > > The cool thing about brainstorming, kicking problems around, is that > ideas evolve and there is usually no one person to credit (or blame.) > > Most people are too insecure to play the game, especially online.I am more than happy to have helped in any small way*. I've never had any problem with making mistakes/ falling down/ saying something thing stupid. It's my #1 method of learning. Basically my electronics life is a list of all the mistakes I have made. (I've made a few mistakes twice, which is embarrassing, you look in your data book.. I had this working before.. dang, head slap.) Reading about someone else's mistakes, just allows me to recognize it more quickly when I do the same thing for the first time. The great thing about electronics, is the result is right there in front of you. (on the 'scope or whatever.) George H. *I can point to a few JL suggestions that we're now selling, (you know a lot of good parts. :^)> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
Reply by ●September 13, 20182018-09-13
On Thursday, September 13, 2018 at 8:22:19 PM UTC-4, pcdh...@gmail.com wrote:> >The cool thing about brainstorming, kicking problems around, is that > >ideas evolve and there is usually no one person to credit (or blame.) > > Brainstorming as originally defined has a bunch of rules that I can't even remember. Inventing stuff with a few smart people and a white board is the most fun you can have standing up. Part of what I do is to teach people the rhythm of doing that. > > >Most people are too insecure to play the game, especially online. > > Depends a lot on the environment. You need a reasonably thick skin unless you've been round long enough to know who you're dealing with. ;) > > Cheers > > Phil HobbsYou also need smart advice/criticism.. That's what I mostly count on SED for, so far, so good. George H.
Reply by ●September 14, 20182018-09-14
On 9/13/18 9:28 PM, George Herold wrote:> On Thursday, September 13, 2018 at 8:22:19 PM UTC-4, pcdh...@gmail.com wrote: >>> The cool thing about brainstorming, kicking problems around, is that >>> ideas evolve and there is usually no one person to credit (or blame.) >> >> Brainstorming as originally defined has a bunch of rules that I can't even remember. Inventing stuff with a few smart people and a white board is the most fun you can have standing up. Part of what I do is to teach people the rhythm of doing that. >> >>> Most people are too insecure to play the game, especially online. >> >> Depends a lot on the environment. You need a reasonably thick skin unless you've been round long enough to know who you're dealing with. ;) >> >> Cheers >> >> Phil Hobbs > > You also need smart advice/criticism.. > That's what I mostly count on SED for, so far, so good. > > George H. >Me too. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●September 14, 20182018-09-14
On Thu, 13 Sep 2018 18:28:49 -0700 (PDT), George Herold <gherold@teachspin.com> wrote:>On Thursday, September 13, 2018 at 8:22:19 PM UTC-4, pcdh...@gmail.com wrote: >> >The cool thing about brainstorming, kicking problems around, is that >> >ideas evolve and there is usually no one person to credit (or blame.) >> >> Brainstorming as originally defined has a bunch of rules that I can't even remember. Inventing stuff with a few smart people and a white board is the most fun you can have standing up. Part of what I do is to teach people the rhythm of doing that. >> >> >Most people are too insecure to play the game, especially online. >> >> Depends a lot on the environment. You need a reasonably thick skin unless you've been round long enough to know who you're dealing with. ;) >> >> Cheers >> >> Phil Hobbs > >You also need smart advice/criticism.. >That's what I mostly count on SED for, so far, so good. > >George H.There are some pretty nasty people here, who don't seem to design electronics, or are too paranoid to discuss it. Ignore them. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●September 14, 20182018-09-14
On Thu, 13 Sep 2018 18:16:08 -0700 (PDT), George Herold <gherold@teachspin.com> wrote:>On Thursday, September 13, 2018 at 3:34:07 PM UTC-4, John Larkin wrote: >> On Wed, 12 Sep 2018 17:53:50 -0700 (PDT), George Herold >> <gherold@teachspin.com> wrote: >> >> >On Wednesday, September 12, 2018 at 8:09:49 PM UTC-4, John Larkin wrote: >> >> On Wed, 12 Sep 2018 16:26:08 -0700 (PDT), George Herold >> >> <gherold@teachspin.com> wrote: >> >> >> >> >On Wednesday, September 12, 2018 at 3:26:42 PM UTC-4, John Larkin wrote: >> >> >> On Wed, 12 Sep 2018 11:16:42 -0700 (PDT), George Herold >> >> >> <gherold@teachspin.com> wrote: >> >> >> >> >> >> >On Wednesday, September 12, 2018 at 11:45:38 AM UTC-4, John Larkin wrote: >> >> >> >> ADA4522 is an amazing amp. 55 volt supplies, low noise, 5 uV max >> >> >> >> offset, EMI hardened, pA bias current. But it has a hangup mode as a >> >> >> >> follower: if the output goes to V+ the input back-to-back diodes keep >> >> >> >> both inputs above the legal common-mode range. Pity it's not RRIO. >> >> >> >Huh that is a nice opamp. (Thanks, well slew rate not so snappy) >> >> >> >What do you mean by hangup? >> >> >> >Does it latch? Or take a long time to recover? >> >> >> > >> >> >> >George H. >> >> >> >> >> >> If the customer input is fairly high impedance, like 20K or so, and he >> >> >> briefly blips the voltage high, the input can hang high, even when the >> >> >> customer backs down. >> >> >> >> >> >> It just occurred to us that we could have that stage have a gain of >> >> >> +1.15 or something, which would keep the inverting input away from >> >> >> Vcc. That just needs two resistors and has no zener leakage concerns. >> >> >> We can cal around the gain. >> >> >OK, so a little gain kills it. If you didn't care too much >> >> >about the output impedance.. or you knew what it was driving, >> >> >you could throw away the gain on the output. >> >> >(but you know that...) >> >> >George H. >> >> >> >> I hadn't thought of that but you're right, the voltage at the >> >> inverting input has a gain of 1.000, after the divider. Unfortunately >> >> there is a load downstream. >> >> >> >> Hmmm, I think it works! The downstream load is about 5K, so we just >> >> add one 500 ohm resistor in series with the opamp output. >> >> >> >> https://www.dropbox.com/s/d7cpms6fcde6my2/ADA4522_fix.JPG?raw=1 >> >Huh, well that is not at all what I had in mind, but it >> >meets all the criteria.. constraining voltages. >> >with less parts and no matching. >> > >> >looks OK... even if the 5k ohm is not that firm. >> > >> >GH >> >(sometimes even the blind pig finds an acorn.) >> >> The cool thing about brainstorming, kicking problems around, is that >> ideas evolve and there is usually no one person to credit (or blame.) >> >> Most people are too insecure to play the game, especially online. >I am more than happy to have helped in any small way*. >I've never had any problem with making mistakes/ falling down/ >saying something thing stupid. It's my #1 method of learning.Ditto. Stupid ideas often evolve into great ideas, unless they are murdered at birth.>Basically my electronics life is a list of all the mistakes I have made. >(I've made a few mistakes twice, which is embarrassing, >you look in your data book.. I had this working before.. >dang, head slap.) >Reading about someone else's mistakes, just allows me to >recognize it more quickly when I do the same thing for the first time.It's surprising how many mistakes and failures turn out to be valuable later, sometimes years later. Which is why we document and archive our experiments, even the dumb ones. We assign a project number to every experiment or breadboard, and have a folder on a server, J:\PROTOS\Zxxx where we keep them. We also archive parts tests and notes in our inventory database, in H:\MAX\PDATA.> >The great thing about electronics, is the result is right there >in front of you. (on the 'scope or whatever.)Yes. I pity mechanical and civil and aeronautical engineers who don't have the visibility that we do. I can probe and thermal image every point on a circuit board. The only tricky part is figuring out where the current is going.> >George H. > >*I can point to a few JL suggestions that we're now selling, >(you know a lot of good parts. :^) >You owe me for that! Medium-Dark chocolate is always acceptable compensation. -- John Larkin Highland Technology, Inc lunatic fringe electronics
