Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 33

Circuit 10: NPN transistor B test
Setup information
Install the transistor as shown in Fig. 2.10. Install all other resistors. Now it is time for the jumpers. Connect
the moving-coil instrument. Check the placement on the board again and only then connect the battery.
Experiment
If everything is wired correctly, the moving-coil instrument will show a strong deflection. The deflection
shows the transistor's current amplification factor B. Full scale means B = 500. In our present case the cir-
cuit can be used to determine the current amplification factor of any low power NPN silicon bipolar transis-
tor. The simple design of the moving-coil instrument however, sets limits to its accuracy.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.10.
Components required:
1 x 2N3904 transistor,
1 x 1 MΩ resistor, 1 x 220 Ω
resistor, 1 x 100 Ω resistor,
1 x moving-coil instrument,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.10: NPN transistor B test
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