Constant Current Sources For Leds - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.37 Constant current sources for LEDs

Circuit 88: constant current with FET transistor
Setup information
Install the FET transistor and the three diodes as shown in Fig. 2.88. The three jumper wires are next.
Check the placement on the board again and only then connect the battery.
Experiment
If everything is wired correctly, current will always be high enough for the LEDs to shine bright – even if the
battery voltage has dropped.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.88.
Components required:
1 x J111 FET transistor,
1 x red LED, 1 x green
LED, 1 x yellow LED,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.88: constant current with
FET transistor
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