Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 72

Circuit 49: Discreet 3.7V Zener diode
Setup information
Install the two transistors and the seven resistors as shown in Fig. 2.49. The nine 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
This circuit delivers constant voltage at the output – where the moving-coil instrument is connected – even
at fluctuating battery voltage. It behaves just like a connected Zener diode. Basically, Zener voltage is
defined by the value of the R2 and R3. Our case here we have an output voltage of 3.7 V. The battery voltage
of the may fluctuate between 6V and 9V.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.49.
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Components required:
1 x 2N3904 transistor,
1 x 2N3906 transistor,
2 x 1 kΩ resistors,
2 x 2.2 kΩ resistors,
1 x 10 kΩ resistor,
2 x 22 kΩ resistors,
1 x moving-coil instrument,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.49: Discreet 3.7V Zener
diode