R2R network as a simple digital to analog converter. The 4 upper left switches are the bits from i.e. an microcontroller, with most left switch is the LSB and the most right of the four is the MSB. A DAC circuit was placed as a reference. The reference voltage of both system are 16 volt, so the range is from 0 to 15V. There are two more switches in the top right corner. If both are open you see the output voltage with no load. When you close the left, the load decreases the output voltage. You can calculate the expected voltage at a specific load, but the better way is to use an opamp as an impedance converter. Close the right of the both switches so the opamp get in place, the load at the opamp output, doesn't affect the voltage.
