Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 219

Circuit 196: constant voltage source
Setup information
Install the transistor, the diode and the three resistors as shown in Fig. 2.196. The four jumper wires come
next. Last but not least connect the moving-coil instrument. Check the placement on the board again and
only then connect the battery.
Experiment
Our circuit ensures a constant voltage at the output, even if load resistance and thus current draw changes
greatly. Output voltage is approximately 1.2V, if the load resistance value ranges between 100 Ω and 10 kΩ.
The needle deflection of the moving-coil instrument remains virtually constant, even if different load resist-
ances in the range of 100 Ω to 10 kΩ occur.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.196.
Components required:
1 x 2N3904 transistor,
1 x red LED,
1 x 1 kΩ resistor,
1 x 2.2 kΩ resis-
tor, 1 x resistor (see
Experiment for value),
1 x moving-coil instrument,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.196: constant voltage
source
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