Hi, please i need to know if the calculations for this summing amplifier is correct

Hi, please i need to know if the calculations for this summing amplifier is correct 

You are on the way to sorting it out, however, watch your units, for example, 200mV =0.2V. Additionally,  use m, not M, the two are not interchangeable, look up https://en.wikipedia.org/wiki/Metric_prefixWhy have you changed the resistor values in the schematic, 5, 10, 20, and 50K are all doable in real world values, even if you have to use series and parallel combinations, it makes the calculations simpler, and the DAC more accurate.Cheers,Richard

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Hi Richard thanks,
please take a look at this diagram also 

Hi, as I said, watch you unit multipliers, M is mega, you want m for milli.Where are you getting the value in brackets from, 200mV is 0.2V.The comment has been made before, the way the question has been represented is poor, you just have to work around it. The idea of the values at the output doubling for each bit change in the input table is what you are observing and have come close to answering. I would think that the x-100mV in the answer column should be x*-100mV, the way the initial answers were given.Keeping the input resistors in a binary sequence of 1,2,4 and 8 exactly is important to maintain accuracy, the feed back resistor is not so critical in that respect, all it does is scale the output, although it must be low enough to ensure that the output of the op-amp does not saturate.Cheers,Richard

EphraimI have been trying to post this comment for about a week but it wouldn't let me.  Finally successful.

Your calculations are correct, but please
confirm you saw my last (long) post on your previous question?

I have issues with the following:

- As Richard stated, get your symbols
right.  Volts are V, not v.  Milli- (1/1000) is m. Mega (1000x) is
M.  You let a MV anywhere near an opamp and it will let the smoke
out!  Work on getting this right, I still make occasional mistakes with
symbols and I'm ashamed of it.

- I know I have told you to use preferred
values in other circuits, but a DAC is a precision circuit and here you need to
get the values as near as possible to the given values. And here it is easy - 2
x 10k in parallel is 5k.  2 x 10k in series is 20k.  22k+18k is
40k.  You notice I am using k, not K.  Usually multipliers for values
above 1 have capital letters, but in this case k is kilo- and K is degrees
Kelvin (temperature).  Confusing I know, but you have to get used to it...

- in your first calculation above you have

   (5 kilo ohms) - 810Mv (8V)

   810 mV is 0.81V, not 8 V. 
You will write 8 in your table because the column is headed  Vout x 100mV.  I don't like this - in my response to your
previous question I put the mv values in the table..

- this is an inverting amplifier so the
outputs will be negative, this is not indicated anywhere?

- the column with 40k does not have any 1's in
it, in either of the questions,  so what is the point of having it? 
(This is maybe not your fault - did you get these questions from a teacher or
from a book?  Whatever it was, you need a better one.)

As an aside, a real-life DAC will use a
voltage reference on the input so the input voltage is precisely known. 
You could try this by putting a 7805 (preferably 78L05) voltage regulator
between the +9V and the input to the switches.  Then you should be able to
get exact steps of 100mV on your output.