Instructions

232
2.98 NAND and NOR gates
Circuit 207: NOR gate with LED
Setup information
Install the two transistors, the three diodes and the four resistors as shown in Fig. 2.207. The eighteen
jumper wires come next followed by the jumpers, which serve as switches (shown dashed). For your guid-
ance, we have labelled the switches with high E1, low E1 and high E2, low E2. Check the placement on the
board again and only then connect the battery.
Components required:
2 x 2N3904 transis-
tors, 2 x 1N4148 silicon
diodes, 1 x red LED,
3 x 1 kΩ resistors,
1 x 10 kΩ resistor,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.207: NOR gate with
LED
Experiment
Even if everything is wired correctly, nothing will happen at first. Both “switches” are on low, the LED is
off. The potential at the output is high. The following table, also called truth table, shows what will happen
now at the different switch states.
Input 1 Input 2 Output LED
low low high dark
high low low illuminated
low high low illuminated
high high low illuminated