Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 160

Experiment
If everything is wired correctly, both "switches" are in the low position. The potential at the output is high;
the moving-coil instrument needle is not moving. The following table, also called truth table, shows what
will happen now at the different switch states.
Input 1
low
high
low
high
The states high and low at the inputs are achieved by toggling the respective switch. Unlike the previous
experiment, the states must be wired manually. In digital electronics, such a circuit with the behaviour
described above is known as NAND gate. A tablet or notebook PC contains tens of thousands of those
gates.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.136.
162
Input 2
low
low
high
high
Output
high
high
high
low
Components required:
1 x 2N3904 transis-
tor, 2 x 1N4148 silicon
diodes, 1 x BAT85
Schottky diode,
1 x 4.7 kΩ resistor,
1 x 10 kΩ resistor,
2 x 22 kΩ resistors,
1 x moving-coil instru-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.136: NAND gate with
moving-coil instrument
Moving-coil instrument
no motion
no motion
no motion
full-scale swing