0 to -20v Power Supply Design & Prototype

Hi all, Something very simple here, and need a quick turnaround. I need someone to design and make a working version of a voltage converter. The input voltage can be either +5v or +13.8v (DC) and the output needs to be variable from 0 to -20v (negative) using a 5-10K pot. It needs to be simple, preferably using a dc-dc converter IC already available on the market. This is just for an LCD contrast bias, but I dont have the time to sit down and figure one out. From my tests, current requirement is low, in the region of 5-20mA, but it may be adviseable to have say 100mA on hand (if the LCD spec. changes). It does not need to limit the current to any particular value. You will be experienced in such designs and will have no trouble making something that does this. You will obtain the parts required (which I will re-imburse you for, including any shipping costs), however the component count should be very low. You will assemble this on a piece of vero/stripboard and supply it working. I am based in the UK, so bear in mind shipping (which I will cover). So, I am willing to cover :- - Your time (not exactly a huge amount, as this is very simple) - Parts costs (again, < $10-15 as thats all thats needed) - Shipping costs (from obtaining parts and shipping to me). ## Deliverables 1) Design and build the negative DC power supply detailed above. 2) Supply the working circuit to me via the mail. ## Platform N/A