Eight voltages from three bits
Build a passive R–2R converter and measure its staircase.
Difficulty: Breadboard. Estimated build time: about 35 minutes. 4-line bill of materials. Compare supplier offers when available. Use only 10 kΩ and 20 kΩ resistors to turn a three-bit pattern into a voltage.
Prepare the bench
Use an isolated, regulated 5 V source with a 20 mA current limit and a digital voltmeter with approximately 10 MΩ input resistance. These are bench tools, not included in the shopping list. Disconnect power before changing connections. Confirm breadboard rail continuity and check for supply shorts before powering up.
Build the terminated ladder
Create nodes N2, N1 and N0. Put 10 kΩ between N2–N1 and another 10 kΩ between N1–N0. Put 20 kΩ from each node to its own input B2, B1 or B0. Add a fourth 20 kΩ from N0 to ground as the termination. OUT is N2. Do not omit that terminating resistor.
Give every bit a level
With power off between changes, connect every bit input directly to ground for 0 or +5 V for 1. Never leave a bit input floating. B2 is the most significant bit nearest OUT; B0 is the least significant bit near the termination. Measure OUT with a high-impedance voltmeter only.
Measure all eight steps
For codes 000 through 111, ideal OUT is 0, 0.625, 1.25, 1.875, 2.5, 3.125, 3.75 and 4.375 V. The equation is OUT = 5(B2/2 + B1/4 + B0/8). The top code is below 5 V by one step. Resistor mismatch, supply error and meter loading shift the real readings; this is not a precision DAC.