157
2.61 Low-noise high-impedance input amplifier
Circuit 132:
High-impedance preamplifier
Setup information
Install the two transistors, the eight resistors, the ceramic capacitor and the electrolytic capacitor as shown
in
Fig. 2.132
The nine jumper wires come next. Last but not least, connect the Piezo element. Check the
placement on the board again and only then connect the battery. You can significantly increase the sensitiv-
ity of the Piezo element by using a sound plate or even a sound box. Read more about it in Chap. 1.2.3
Components required:
1 x 2N3906 transistor,
1 x J111 FET transistor,
1 x 1 M
Ω
resistor,
1 x 22 k
Ω
resistor,
1 x 10 k
Ω
resistor,
3 x 2.2 k
Ω
resistor,
1 x 1 k
Ω
resistor, 1 x 100 nF
ceramic capacitor,
1 x 10 μF electrolytic
capacitor, 1 x Piezo ele-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.132:
High-impedance
preamplifier
Experiment
Even if everything is wired correctly, you won’t hear anything at first. If you connect an mp3 player to the
input, loud music will come from the Piezo element, even though you have turned the volume very low. The
input is very high impedance, and when you just touch it with your bare finger you will hear some scraping
and humming sounds .
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.132.
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...
