Which is the right tool to use - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: Which is the right tool to use (/thread-6721.html) Which is the right tool to use - leprechaun - 08-23-2016 11:41 AM Hello guys I am confronted with a problem I can solve just by using the prime as an ordinary calculator but I could imagine that there is a built-in tool for doing the job. Maybe a user program would be an option, but I am so busy at work atm that messing around with the programming does not seem to be a good idea. The problem is that: I need to design several switching supplies with different feedback voltages and different bias currents on them. What I want to solve is: (R1+R2)/R2 == U0/Ufb. U0 is given Ufb is given R2 is given by myself and in the range of, say, 120k..270k. Pre-defining R2 values so that they match E24 would be sugar on top. Is there built-in feature that I can quickly use? thanks RE: Which is the right tool to use - Didier Lachieze - 08-23-2016 12:44 PM You can use the spreadsheet application. See the attached simple example where U0 and Ufb are named cells, column C contains the R2 predefined values (you can put what you want here) and column D has the column-wide formula: "=C:C*((U0/Ufb)-1)" Just enter the values of U0 and Ufb you want to design for and youâ€™ll get in columns C and D the pairs of R2/R1 values. You can customize this spreadsheet as you need. [attachment=3838] [attachment=3837] RE: Which is the right tool to use - leprechaun - 08-24-2016 05:57 AM Thank you for the suggestion!