Forums

Opamp w/ Vsupply >36V

Started by George Herold July 15, 2013
On Tue, 16 Jul 2013 10:15:20 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>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
Take a look at URS2153D. It does all that oscillator/driver stuff. Works great. -- 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 10:15:20 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>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
Here's something smilar, with an ISDN transformer to make 120 volts... https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power.pdf -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
On 07/16/2013 11:11 AM, John Larkin wrote:
> On Tue, 16 Jul 2013 10:15:20 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> 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 > > Take a look at URS2153D. It does all that oscillator/driver stuff. Works great. > > >
I'm using that one too (IRS2153D). I'll probably switch to the quicker one (IRS21531D) because it has 0.6 us dead time instead of 1.5 us. That will let me bump up the frequency and so halve the volt-seconds for a given output power. The little ISDN transformers have leakage inductance below 0.1%. 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 07/16/2013 11:42 AM, John Larkin wrote:
> On Tue, 16 Jul 2013 10:15:20 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> 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 > > Here's something smilar, with an ISDN transformer to make 120 volts... > > https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power.pdf
Thanks. What frequency do you drive it at? 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 07/16/2013 10:24 AM, George Herold wrote:
> On Tuesday, July 16, 2013 9:54:07 AM UTC-4, Phil Hobbs 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. > > Ohh, that's a nice idea.. can I still power the opamp from the LM317 output? > In this case I wanted a new voltage reference after the 'ground' and V(+) were defined by the regulators. I gain up the 1.25V's by factors of 20-30 and 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.) > 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. >
Sure, as long as the LM317's output is enough to wake up the op amp. The output should be more or less an open circuit until the bias comes up, I think, so the 317's output follows its input till you start pulling current out of the resistor string or zener. 317s are pretty slow, so you want to use the split feedback trick with a cap from the op amp output to its inverting input. Cheers Phil -- 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
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.
http://www.apexanalog.com/products/power-operational-amplifiers/
On Tuesday, July 16, 2013 9:31:01 AM UTC-4, 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.
Well what is this stuff about exceeding 36V??? Is it some kind of start-up overshoot?
> 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. >
I had a burn-in oven issue on a 5V part and 8V transorbs were fine. A lot depends on the chip design. Parts with large devices tend to do worse since the field created due to the excess voltage "seeks" a crystal defect. Lots of active area means more chances to find that defect. Most electromigration rules are generous enough that you don't see metal failure due to overvoltage. So the routing area doesn't count.
> Older analog processes, like for classic 741 and LF353 types, would > fail way past ratings, numbers like 60 volts. Newer parts cut things > tighter. Or maybe specmanship has got more intense. > > > >
That part is bipolar on SOI. You would think the active circuitry would benefit from the insulator, but I have no first hand knowledge of that. [Usually a reversed bias diode is what fails in overvoltage.] But the part is cutting edge, so I can see the tolerances being tight.
On Tue, 16 Jul 2013 13:24:51 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 07/16/2013 11:42 AM, John Larkin wrote: >> On Tue, 16 Jul 2013 10:15:20 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> 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 >> >> Here's something smilar, with an ISDN transformer to make 120 volts... >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/ESM/ESM_power.pdf > >Thanks. > >What frequency do you drive it at?
100K, from the chart on the data sheet! -- 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