Forums

Opamp w/ Vsupply >36V

Started by George Herold July 15, 2013
On Mon, 15 Jul 2013 17:35:22 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

>On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >> Opamp Vsupply >36V >> > >Fix your power supply and use readily available, and commonly used, OAs.
Or add a discrete component buffer to a garden-variety OpAmp. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wrote:
> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: > > > Opamp Vsupply >36V > > > > > > > Fix your power supply and use readily available, and commonly used, OAs.
Ahh, well there's nothing wrong with the supply. I just need 30V of stable bias. The LM317's had too much drift and so I've now got a 10 Volt reference gained up to 30V. George H.
On 07/16/2013 09:31 AM, George Herold wrote:
> On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wrote: >> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >> >>> Opamp Vsupply >36V >> >>> >> >> >> >> Fix your power supply and use readily available, and commonly used, OAs. > > Ahh, well there's nothing wrong with the supply. I just need 30V of stable bias. The LM317's had too much drift and so I've now got a 10 Volt reference gained up to 30V. > > George H. >
Might be cheaper to use the 317 inside an op amp loop. The op amp can run at low voltage then. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Tue, 16 Jul 2013 09:54:07 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 07/16/2013 09:31 AM, George Herold wrote: >> On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wrote: >>> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >>> >>>> Opamp Vsupply >36V >>> >>>> >>> >>> >>> >>> Fix your power supply and use readily available, and commonly used, OAs. >> >> Ahh, well there's nothing wrong with the supply. I just need 30V of stable bias. The LM317's had too much drift and so I've now got a 10 Volt reference gained up to 30V. >> >> George H. >> > >Might be cheaper to use the 317 inside an op amp loop. The op amp can >run at low voltage then. > >Cheers > >Phil Hobbs
A 317, or an LM1117, makes a great power stage. It still current and thermal limits. You can put a zener in series with the adjust pin so the opamp only has to swing a few volts. Then you can power the opamp from the 1117 *output*. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Le Tue, 16 Jul 2013 06:31:01 -0700, George Herold a &eacute;crit:

> On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com > wrote: >> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >> >> > Opamp Vsupply >36V >> >> >> > >> >> >> Fix your power supply and use readily available, and commonly used, >> OAs. > > Ahh, well there's nothing wrong with the supply. I just need 30V of > stable bias. The LM317's had too much drift and so I've now got a 10 > Volt reference gained up to 30V. >
LTC6090 should have enough margin I suppose :-) Lots of high supply voltage opamps at Linear. Twelve seems to meet your criterias. -- Thanks, Fred.
On 07/16/2013 09:58 AM, John Larkin wrote:
> On Tue, 16 Jul 2013 09:54:07 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 07/16/2013 09:31 AM, George Herold wrote: >>> On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wrote: >>>> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >>>> >>>>> Opamp Vsupply >36V >>>> >>>>> >>>> >>>> >>>> >>>> Fix your power supply and use readily available, and commonly used, OAs. >>> >>> Ahh, well there's nothing wrong with the supply. I just need 30V of stable bias. The LM317's had too much drift and so I've now got a 10 Volt reference gained up to 30V. >>> >>> George H. >>> >> >> Might be cheaper to use the 317 inside an op amp loop. The op amp can >> run at low voltage then. >> >> Cheers >> >> Phil Hobbs > > A 317, or an LM1117, makes a great power stage. It still current and thermal > limits. You can put a zener in series with the adjust pin so the opamp only has > to swing a few volts. Then you can power the opamp from the 1117 *output*.
I've often used 317s to run temperature control loops, where I could make the heater run on high enough voltage that the 3V dropout didn't kill me. LM1117s have half the dropout, which helps. Re higher voltage supplies: I just built one of those self-oscillating half-bridge supplies with a 1CT : 2CT ISDN transformer wired as an autotransformer. Unloaded, it saturates at about 750 V*us, and at 150 kHz it puts out a watt or two at +-50V with + and - voltage doublers. The half-bridge topology has one nasty feature--if the core saturates just once, it instantly discharges the coupling cap, which doubles the volt-seconds on the next half cycle, so it saturates on every half cycle thereafter until the FETs cook. That needs a bandage or else a 2:1 derating of the volt-seconds, which is a pain. Alternatively I suppose I could just reduce the size of the coupling cap, which hurts the maximum power output. (I suppose there's a Royer-style solution there somewhere as well, but I'm using both windings for other things.) No sound effects this time, but I've officially joined Joerg's FET demolition derby club. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Tuesday, July 16, 2013 9:54:07 AM UTC-4, Phil Hobbs wrote:
> On 07/16/2013 09:31 AM, George Herold wrote: >=20 > > On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wro=
te:
>=20 > >> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >=20 > >> >=20 > >>> Opamp Vsupply >36V >=20 > >> >=20 > >>> >=20 > >> >=20 > >> >=20 > >> >=20 > >> Fix your power supply and use readily available, and commonly used, OA=
s.
>=20 > > >=20 > > Ahh, well there's nothing wrong with the supply. I just need 30V of st=
able bias. The LM317's had too much drift and so I've now got a 10 Volt re= ference gained up to 30V.
>=20 > > >=20 > > George H. >=20 > > >=20 >=20 >=20 > Might be cheaper to use the 317 inside an op amp loop. The op amp can=20 >=20 > run at low voltage then.
Ohh, that's a nice idea.. can I still power the opamp from the LM317 outpu= t? =20 In this case I wanted a new voltage reference after the 'ground' and V(+) w= ere defined by the regulators. I gain up the 1.25V's by factors of 20-30 a= nd any change in the 1.25 V gets magnified. Once I get the 30 volt bias I'= d like it stable to ~1mV or so. (For maybe 10 minutes to an hour.)=20 So anyway the current circuit works fine... (the pcb is spun and in the box= .) I don't want to redo it. I guess I should think of all the gotcha's before= doing the design.=20 George H.
>=20 >=20 >=20 > Cheers >=20 >=20 >=20 > Phil Hobbs >=20 >=20 >=20 > --=20 >=20 > Dr Philip C D Hobbs >=20 > Principal Consultant >=20 > ElectroOptical Innovations LLC >=20 > Optics, Electro-optics, Photonics, Analog Electronics >=20 >=20 >=20 > 160 North State Road #203 >=20 > Briarcliff Manor NY 10510 >=20 >=20 >=20 > hobbs at electrooptical dot net >=20 > http://electrooptical.net
On Tuesday, July 16, 2013 9:58:59 AM UTC-4, John Larkin wrote:
> On Tue, 16 Jul 2013 09:54:07 -0400, Phil Hobbs > > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > > > >On 07/16/2013 09:31 AM, George Herold wrote: > > >> On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wrote: > > >>> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: > > >>> > > >>>> Opamp Vsupply >36V > > >>> > > >>>> > > >>> > > >>> > > >>> > > >>> Fix your power supply and use readily available, and commonly used, OAs. > > >> > > >> Ahh, well there's nothing wrong with the supply. I just need 30V of stable bias. The LM317's had too much drift and so I've now got a 10 Volt reference gained up to 30V. > > >> > > >> George H. > > >> > > > > > >Might be cheaper to use the 317 inside an op amp loop. The op amp can > > >run at low voltage then. > > > > > >Cheers > > > > > >Phil Hobbs > > > > A 317, or an LM1117, makes a great power stage. It still current and thermal > > limits. You can put a zener in series with the adjust pin so the opamp only has > > to swing a few volts. Then you can power the opamp from the 1117 *output*.
Got it.. that's good to know. I've used the LM395 as an opamp power booster.. I think Jim T. said that the guts are similar to a 317. Hmm I don't need any power I could have just stuck almost any transistor on the output. OK maybe next time. George H.
> > > > > > > > > > -- > > > > John Larkin Highland Technology Inc > > www.highlandtechnology.com jlarkin at highlandtechnology dot com > > > > Precision electronic instrumentation > > Picosecond-resolution Digital Delay and Pulse generators > > Custom timing and laser controllers > > Photonics and fiberoptic TTL data links > > VME analog, thermocouple, LVDT, synchro, tachometer > > Multichannel arbitrary waveform generators
On Tue, 16 Jul 2013 07:34:24 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Tuesday, July 16, 2013 9:58:59 AM UTC-4, John Larkin wrote: >> On Tue, 16 Jul 2013 09:54:07 -0400, Phil Hobbs >> >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >> >> >> >On 07/16/2013 09:31 AM, George Herold wrote: >> >> >> On Monday, July 15, 2013 8:35:22 PM UTC-4, bloggs.fred...@gmail.com wrote: >> >> >>> On Monday, July 15, 2013 12:01:21 PM UTC-4, George Herold wrote: >> >> >>> >> >> >>>> Opamp Vsupply >36V >> >> >>> >> >> >>>> >> >> >>> >> >> >>> >> >> >>> >> >> >>> Fix your power supply and use readily available, and commonly used, OAs. >> >> >> >> >> >> Ahh, well there's nothing wrong with the supply. I just need 30V of stable bias. The LM317's had too much drift and so I've now got a 10 Volt reference gained up to 30V. >> >> >> >> >> >> George H. >> >> >> >> >> > >> >> >Might be cheaper to use the 317 inside an op amp loop. The op amp can >> >> >run at low voltage then. >> >> > >> >> >Cheers >> >> > >> >> >Phil Hobbs >> >> >> >> A 317, or an LM1117, makes a great power stage. It still current and thermal >> >> limits. You can put a zener in series with the adjust pin so the opamp only has >> >> to swing a few volts. Then you can power the opamp from the 1117 *output*. > >Got it.. that's good to know. >I've used the LM395 as an opamp power booster.. I think Jim T. said that the guts are similar to a 317. Hmm I don't need any power I could have just stuck almost any transistor on the output. OK maybe next time. > >George H. >>
[snip] Yep. Very same silicon. Just a minor change in metalization, I reverse-engineered it and wrote a report for ICE _many_ moons ago... http://www.analog-innovations.com/SED/ICE-LM195-LM117.pdf ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Mon, 15 Jul 2013 12:24:47 -0700, miso <miso@sushi.com> wrote:

>On 7/15/2013 11:12 AM, Spehro Pefhany wrote: >> On Mon, 15 Jul 2013 09:52:53 -0700, John Larkin >> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>> >>> If it's rated 36 max, use it up to 36. The manufacturer has already factored in >>> the headroom. >> >> Make sure there are no transients possible on the power supplies etc. >> if you do this. I once had a really horrible experience using 16V TI >> CMOS op-amps at the system supplies of +/-8V (almost 1% failure rate). >> > >You can get a lot of soft failures due to overstress, but the part keeps >"working." A soft failure in a chip is something like the shutdown >current out of spec or the input impedance is low, etc. Often chips have >soft failures and nobody notices. For instance, a bit of increased >shutdown current can be lost if there are a lot of parts on the board. A >lower impedance on an input may not matter if the rest of the components >are low impedance. > >But your problem sheds light on an interesting test problem, namely >absmax. There is no standard on how to test parts beyond their datasheet >limits. Some companies only QA absmax. They stress the part and see if >it still meets spec when used at stated voltages. Others do a real >absmax test, but not at strict electrical limits. But then there is the >question of should you be stressing your parts at all? > >But to get 99% failure when operated at the datasheet limits implies to
99% non-failure rate. Still terrible.
>me a part that has other problems rather than your supply being the >culprit. There is a lot of margin in absmax. > >That said, transorb diodes are highly recommended!
A TVS that is suitable for 16V nominal (wg. SA16A or SA17A) can have
>> 20V across it if it's clamping a significant current, so it's not
much of a solution for a marginal situation. It's great if the chip can actually stand 30V momentarily.