Need Op Amp for design

On 2017-11-24 14:28, Leslie Rhorer wrote:
>>>
>>> Am I wrong?  If not, is there a different choice of high input
>>> impedance op amp that can withstand up to 25V when power is shut
>>> off?
>>
>> You should buy a battery management IC, some of them handle lots of
>> cells, and this is especially true of Li batteries. There are
>> physics based considerations that dwarf the triviality of the
>> electronics interconnection topology.
>
> I am using an off-the shelf LiPo battery monitor specifically
> designed to monitor LiPo batteries during use.  These are extremely
> common in the Radio Control hobby sector, and are readily available
> at very low cost.  Below is an example.  The only problem is these
> are designed to be manually disconnected when not in use.


The good ones don't. Read up about "ship mode". I brought you an example 
in another post.

[...]

-- 
Regards, Joerg

http://www.analogconsultants.com/

On Friday, November 24, 2017 at 4:48:01 PM UTC-5, John Larkin wrote:
> On Fri, 24 Nov 2017 12:38:20 -0800 (PST),
> bloggs.fredbloggs.fred@gmail.com wrote:
> 
> >On Tuesday, November 21, 2017 at 2:35:27 PM UTC-5, Winfield Hill wrote:
> >> John Larkin wrote...
> >> >
> >> > The ancient LM324 has PNP input transistors, and the
> >> > safe input voltages can go to +32 irrespective of V+.
> >> 
> >>  I also thought of PNP-input single-supply op-amps as
> >>  a good solution, but the O.P. seems not to notice.
> >> 
> >> 
> >> -- 
> >>  Thanks,
> >>     - Win
> >
> >Weren't those the original phase inversion cheapos? Meaning you could end up with anything powering them up with a live input.
> 
> I don't know of any problems with the original LM324.

Have it your way...

http://www.analog.com/media/en/training-seminars/tutorials/MT-036.pdf

> 
> Except the ghastly crossover distortion.
> 
> And the pitiful slew rate.
> 
> And the wimpy drive.
> 
> And the horrible stuff that happens if any of the inputs go below
> ground.
> 
> The LM709 had front-end zener quirks.


> 
> 
> -- 
> 
> John Larkin   Highland Technology, Inc   trk
> 
> jlarkin att highlandtechnology dott com
> http://www.highlandtechnology.com

bloggs.fredbloggs.fred@gmail.com wrote...
>
>On Friday, November 24, 2017 at 4:48:01 PM UTC-5, John Larkin wrote:
>> On Fri, 24 Nov 2017 12:38:20 -0800 (PST),
>> bloggs.fredbloggs.fred@gmail.com wrote:
>> 
>>> On Tuesday, November 21, 2017, Winfield Hill wrote:
>>>> John Larkin wrote...
>>>> >
>>>> > The ancient LM324 has PNP input transistors, and the
>>>> > safe input voltages can go to +32 irrespective of V+.
>>>> 
>>>>  I also thought of PNP-input single-supply op-amps as
>>>>  a good solution, but the O.P. seems not to notice.
>>>
>>> Weren't those the original phase inversion cheapos?
>>> Meaning you could end up with anything powering them up with a live input.
>> 
>> I don't know of any problems with the original LM324.
>
> Have it your way...
>
>http://www.analog.com/media/en/training-seminars/tutorials/MT-036.pdf

 The issues discussed there don't apply to the LM324, when
 used with input voltages between Vee - 0.3V and Vee +32V.


-- 
 Thanks,
    - Win

On 2017-11-25 09:00, Winfield Hill wrote:
> bloggs.fredbloggs.fred@gmail.com wrote...
>>
>> On Friday, November 24, 2017 at 4:48:01 PM UTC-5, John Larkin wrote:
>>> On Fri, 24 Nov 2017 12:38:20 -0800 (PST),
>>> bloggs.fredbloggs.fred@gmail.com wrote:
>>>
>>>> On Tuesday, November 21, 2017, Winfield Hill wrote:
>>>>> John Larkin wrote...
>>>>>>
>>>>>> The ancient LM324 has PNP input transistors, and the
>>>>>> safe input voltages can go to +32 irrespective of V+.
>>>>>
>>>>>   I also thought of PNP-input single-supply op-amps as
>>>>>   a good solution, but the O.P. seems not to notice.
>>>>
>>>> Weren't those the original phase inversion cheapos?
>>>> Meaning you could end up with anything powering them up with a live input.
>>>
>>> I don't know of any problems with the original LM324.
>>
>> Have it your way...
>>
>> http://www.analog.com/media/en/training-seminars/tutorials/MT-036.pdf
>
>   The issues discussed there don't apply to the LM324, when
>   used with input voltages between Vee - 0.3V and Vee +32V.
>

So how much leakage current will there be on a non-ST-"A" version if an 
input is connected to, say, 24V while V+ is zero or open?

-- 
Regards, Joerg

http://www.analogconsultants.com/

On Friday, 24 November 2017 01:54:53 UTC, David Eather  wrote:
> On Fri, 24 Nov 2017 01:54:57 +1000, Joerg <news@analogconsultants.com>  
> wrote:
> 
> > On 2017-11-22 22:22, Jasen Betts wrote:
> >> On 2017-11-21, Joerg <news@analogconsultants.com> wrote:
> >>> On 2017-11-21 11:35, Winfield Hill wrote:
> >>>> John Larkin wrote...
> >>>>>
> >>>>> The ancient LM324 has PNP input transistors, and the
> >>>>> safe input voltages can go to +32 irrespective of V+.
> >>>>
> >>>
> >>> The datasheet says "Don't do that" though. Looking at the innards on
> >>> page 4 it seems you'd hit a diode path to V+:
> >>>
> >>> http://www.st.com/content/ccc/resource/technical/document/datasheet/bd/fc/46/43/26/8f/40/7f/CD00001046.pdf/files/CD00001046.pdf/jcr:content/translations/en.CD00001046.pdf
> >>
> >> use the TI part.
> >>
> >> http://www.ti.com/lit/ds/snosc16d/snosc16d.pdf
> >>
> 
> There is also a lower power version of the lm324 / 358 from ti. It's  
> imaginatively called an LP324 and LP358

beware lesser performance though.

On Saturday, 25 November 2017 00:09:27 UTC, John Larkin  wrote:
> On Fri, 24 Nov 2017 14:06:48 -0800 (PST), Leslie Rhorer
> <rhorerles@gmail.com> wrote:
> >On Friday, November 24, 2017 at 3:48:01 PM UTC-6, John Larkin wrote:
> >> I don't know of any problems with the original LM324.
> >> 
> >> Except the ghastly crossover distortion.
> >> 
> >> And the pitiful slew rate.
> >> 
> >> And the wimpy drive.
> >> 
> >> And the horrible stuff that happens if any of the inputs go below
> >> ground.
> >
> >None of which matter in this situation, which is one reason why your original suggestion is definitely the front runner.  I've ordered a couple of Op Amps, including a 324, from Mouser for testing.  They should arrive Monday.
> 
> One other quirk: if one of the four opamps rails, it can mess up the
> other three. Shared current sources. I don't remember just how bad
> that is.

I love the 324, it's cheap & very useful. Crossover is easily avoided. Don't buy Motorola or bias the output.

But I do wish there were even cheaper opamps with even more corners cut. There must be plenty of uses for opamps with major compromises, eg poor gain. Trouble is things start expensive and drop in price, which would make cruder opamps uncompetitive in the early days. And who wants to sell an even cheaper chip when they can introduce a high ticket one.


NT

On Sat, 25 Nov 2017 17:28:49 -0800 (PST), tabbypurr@gmail.com wrote:

>On Saturday, 25 November 2017 00:09:27 UTC, John Larkin  wrote:
>> On Fri, 24 Nov 2017 14:06:48 -0800 (PST), Leslie Rhorer
>> <rhorerles@gmail.com> wrote:
>> >On Friday, November 24, 2017 at 3:48:01 PM UTC-6, John Larkin wrote:
>> >> I don't know of any problems with the original LM324.
>> >> 
>> >> Except the ghastly crossover distortion.
>> >> 
>> >> And the pitiful slew rate.
>> >> 
>> >> And the wimpy drive.
>> >> 
>> >> And the horrible stuff that happens if any of the inputs go below
>> >> ground.
>> >
>> >None of which matter in this situation, which is one reason why your original suggestion is definitely the front runner.  I've ordered a couple of Op Amps, including a 324, from Mouser for testing.  They should arrive Monday.
>> 
>> One other quirk: if one of the four opamps rails, it can mess up the
>> other three. Shared current sources. I don't remember just how bad
>> that is.
>
>I love the 324, it's cheap & very useful. Crossover is easily avoided. Don't buy Motorola or bias the output.
>
>But I do wish there were even cheaper opamps with even more corners cut. There must be plenty of uses for opamps with major compromises, eg poor gain. Trouble is things start expensive and drop in price, which would make cruder opamps uncompetitive in the early days. And who wants to sell an even cheaper chip when they can introduce a high ticket one.

NJR seems to make a business of it.  There's always someone who wants
junk.  And someone who will buy it.

On Saturday, November 25, 2017 at 5:28:53 PM UTC-8, tabb...@gmail.com wrote:

> I love the 324, it's cheap & very useful. Crossover is easily avoided. Don't buy Motorola or bias the output.
> 
> But I do wish there were even cheaper opamps with even more corners cut. 

The ST variant exemplifies why you don't see those; a different op amp has to compete for
the bottom dollar, which is a slow-to-pay-back plan.   So, different or not, a low-end
quad op amp gets "LM324" name attached to it, which is how one advertises
the low-end amp while not using an advertising budget.

It has to show up in a quick search for that part number...

On Saturday, November 25, 2017 at 8:48:01 AM UTC+11, John Larkin wrote:
> On Fri, 24 Nov 2017 12:38:20 -0800 (PST),
> bloggs.fredbloggs.fred@gmail.com wrote:
> 
> >On Tuesday, November 21, 2017 at 2:35:27 PM UTC-5, Winfield Hill wrote:
> >> John Larkin wrote...
> >> >
> >> > The ancient LM324 has PNP input transistors, and the
> >> > safe input voltages can go to +32 irrespective of V+.
> >> 
> >>  I also thought of PNP-input single-supply op-amps as
> >>  a good solution, but the O.P. seems not to notice.
> >> 
> >> 
> >> -- 
> >>  Thanks,
> >>     - Win
> >
> >Weren't those the original phase inversion cheapos? Meaning you could end up with anything powering them up with a live input.
> 
> I don't know of any problems with the original LM324.
> 
> Except the ghastly crossover distortion.
> 
> And the pitiful slew rate.
> 
> And the wimpy drive.
> 
> And the horrible stuff that happens if any of the inputs go below
> ground.
> 
> The LM709 had front-end zener quirks.

The LM709 had a conventional NPN long-tailed pair as it's input. If you put more than 5V across the inputs one or other base-emitter junction broke down - the voltage is a bit high for a pure Zener breakdown, but reverse-biassing a base-emitter junction to breakdown down damages the base-emitter junction even if it doesn't destroy it.

The data sheet was perfectly explicit about the voltage difference limit between the inputs - it might not have been a feature, but it definitely wasn't a quirk.

Bob Widlar got more ingenious later, and subsequent op amps either used an input stage that could take more volts, or protected the input stage with inverse parallel diodes.

-- 
Bill Sloman, Sydney

On Sat, 25 Nov 2017 17:28:49 -0800 (PST), tabbypurr@gmail.com wrote:

>On Saturday, 25 November 2017 00:09:27 UTC, John Larkin  wrote:
>> On Fri, 24 Nov 2017 14:06:48 -0800 (PST), Leslie Rhorer
>> <rhorerles@gmail.com> wrote:
>> >On Friday, November 24, 2017 at 3:48:01 PM UTC-6, John Larkin wrote:
>> >> I don't know of any problems with the original LM324.
>> >> 
>> >> Except the ghastly crossover distortion.
>> >> 
>> >> And the pitiful slew rate.
>> >> 
>> >> And the wimpy drive.
>> >> 
>> >> And the horrible stuff that happens if any of the inputs go below
>> >> ground.
>> >
>> >None of which matter in this situation, which is one reason why your original suggestion is definitely the front runner.  I've ordered a couple of Op Amps, including a 324, from Mouser for testing.  They should arrive Monday.
>> 
>> One other quirk: if one of the four opamps rails, it can mess up the
>> other three. Shared current sources. I don't remember just how bad
>> that is.
>
>I love the 324, it's cheap & very useful. Crossover is easily avoided. Don't buy Motorola or bias the output.
>
>But I do wish there were even cheaper opamps with even more corners cut. There must be plenty of uses for opamps with major compromises, eg poor gain. Trouble is things start expensive and drop in price, which would make cruder opamps uncompetitive in the early days. And who wants to sell an even cheaper chip when they can introduce a high ticket one.
>
>
>NT

The Diodes Inc version of the LM324 is 6.5 cents, Digikey price by the
reel. Under 2 cents per opamp. 

What does Digikey pay? 5 cents? Why does anybody bother to make and
package a quad opamp for 5 cents?

When these were new, one cost about as much as a couple of bicycles.

https://www.dropbox.com/s/9idlgfug24rqxyb/Philbricks.jpg?raw=1




-- 

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com