132
2.47 Constant current source
Circuit 107:
constant current source 1.2 mA
Setup information
Install the two transistors and the six resistors as shown in
Fig. 2.107.
Then insert the eight jumpers. Check
the placement on the board again and only then connect the battery.
Components required:
2 x 2N3904 transistors,
1 x 47
Ω
resistor,
1 x 2.2 k
Ω
resistor,
2 x 10 k
Ω
resistors,
1 x 47 k
Ω
resis-
tor, 1 x resistor (see
Experiment for value),
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.107:
constant current
source 1.2 mA
Experiment
A digital multimeter’s constant current source ensures that the value of resistors can be measured. In our
circuit you could use any value between 100
Ω
and 1 k
Ω
for R5. The current flowing through this resistor is
always 1.2 mA. Since the resistance value is calculated by voltage divided by current according to Ohm ‘s
law, a voltage measurement will do. You can measure the voltage at R5 using a multimeter and calculate
the resistance value using the current (1.2 mA), which we already know.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.107.
Summary of Contents for ELECTRONICS EXPERIMENTS BOX
Page 4: ......
Page 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Page 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Page 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Page 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
