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lm7321 substitute

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kohleh(at)yahoo.com
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Posted: Thu May 01, 2014 8:32 am Post subject: lm7321 substitute

Earlier in the thread I saw a mention of a rail to rail input requirement. If that is still needed, note the common mode input voltage range of Vdd - 1.35 volts maximum for the TLV27x. Seems to indicate the input range is not really rail to rail and I'd expect the output to swing hard to the full on supply voltage whenever the input is within 1.35v of the supply voltage. 

Ken

On 30/04/2014 4:35 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)aeroelectric.com>

 At 03:13 PM 4/30/2014, you wrote:

> 

> The opamp should be rated at least 15v min.

     Okay, this one should work

 http://tinyurl.com/llsm37s

     Let me know how this works for you . . . I'll

     revise my document on the website. I could

     also whack out a little ecb that would sit

     between the solder-cups on a d-sub and make

     it a whole lot easier to package . . .

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nuckolls.bob(at)aeroelect
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Posted: Sat May 03, 2014 6:03 pm Post subject: lm7321 substitute

At 11:31 AM 5/1/2014, you wrote:

 	  Quote: 	
		  



Earlier in the thread I saw a mention of a rail to rail input 

requirement. If that is still needed, note the common mode input 

voltage range of Vdd - 1.35 volts maximum for the TLV27x. Seems to 

indicate the input range is not really rail to rail and I'd expect 

the output to swing hard to the full on supply voltage whenever the 

input is within 1.35v of the supply voltage.



Ken


	


   Good catch . . . thought I had that covered. After several

   asphalt meditations last week, I came to the conclusion

   that while the rail-to-rail i/o buffer would offer

   a 'simple' solution, it wasn't very elegant.



   I'm working on a drawing that uses a R-t-R output op

   amp in an inverting configuration which does two good

   things for us. (1) We can add pots that set gain and

   offset such that the builder can exploit ALL the

   bars in the trim indicator display even if the pot doesn't

   run full mechanical stroke and (2) we can drive any

   number of indicators from the single amplifier.



   Refresh my memory . . . does the orange lead on

   a RayAllen bar graph display output 5 volts or something

   else?



   Ken, thanks for the heads-up . . .

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat May 17, 2014 8:51 am Post subject: lm7321 substitute

I'm working on a drawing that uses a R-t-R output op

   amp in an inverting configuration which does two good

   things for us. (1) We can add pots that set gain and

   offset such that the builder can exploit ALL the

   bars in the trim indicator display even if the pot doesn't

   run full mechanical stroke and (2) we can drive any

   number of indicators from the single amplifier.



---------------



   Sorry I dropped the ball on this. I'm wrestling with

   a computer with a dying operating system . . . it's

   had some 'quirks' for a couple years but I'm now

   contemplating a new build with Win7 . . . not exactly

   the way I'd like to blow away a day's worth of praying

   over a new computer!



   In any case, here's the drawing



http://tinyurl.com/nmftvll



   By eliminating the not-well-considered goal of

   rail-to-rail input and output, crafting an inverting

   amplifier with R-t-R output offers some features

   cited above that seem to make it a better approach.

   Further, all the parts are available as thru-hole.



   This would be a candidate for packaging in a 15-pin

   d-sub housing which is what I've illustrated

   with pin numbers arbitrarily assigned to a board-edge

   connector . . . obviously, one might perf-board this

   circuit as well . . .

   Bob . . .

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