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AND gate from diodes

Logic Gates from Components · free online experiment, runs in your browser with no install or sign-up.

Open this experiment in the circuit simulator

Objective

Build an AND gate from two diodes and a pull-up resistor and check its truth table.

Procedure

Use the Controls tab (or the batteries' Properties) to set each input to 0 V or 5 V and press Start Simulation; turn Live on and drag an input slider to watch the output.

Theory

The lower input pulls the output down to Vin + 0.7 V through its diode; only when both inputs are high is the output pulled up to 5 V by the resistor (diodes reverse-biased). A '0' input therefore gives 0.7 V.

Questions to answer

What happens to the low level if you cascade two of these gates?

Components used

3 × Battery / DC source, 2 × Diode 1N4007, Panel voltmeter, Resistor 220 ohm 1/4W

About the model

Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.