Instructions

145
2.55 Electronic potentiometer
Circuit 120: Electronic level control
Setup information
Install the two transistors, the three resistors and the two electrolytic capacitors as shown in Fig. 2.120
followed by a jumper wire. Check the placement on the board again before you start with your experiment
and only then connect the battery.
Components required:
1 x J111 FET transistor,
1 x 220 kΩ resistor,
1 x 100 Ω resistor,
1 x 10 kΩ resistor,
1 x 10 μF electro-
lytic capacitor,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.120: Electronic level
control
Experiment
An electronic level control is used to determine the weakening of an audio signal by means of the control
voltage value. In our present case, at 0 V control voltage, the audio signal will be damped by the factor 100;
at -5 V control voltage will be muted by Factor 2. The maximum output voltage is about 1 V. As sources for
the (negative) control voltage you could use batteries such as 1.5V, 3V, 4.5V batteries or a suitable variable
power supply.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.120.