Low-Impedance Microphone Preamp

This amplifier uses a common-gate FET amplifier to match a low-Z microphone.

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Sound Mixer/Amplifier

Both input signals can be independently controlled by VR1 and VR2. The balance control VR3 is used to fade out one signal while simultaneously fading in the other. The transistor provides gain and the combined output signal level is controlled by VR4.

Audio Fader

In this circuit Q1 is a simple amplifier that has its gain controlled by a variable emitter resistance supplied by FET Q2. In the up position of SI. C3 discharges through R5 and the gain of Q1 decreases because Q2 is driven toward cut-off. In the down position, Q2 conducts more, depending on the setting of R6. which causes a gain increase. By varying R5 or C3, various fade rates can be obtained.

2N2369: Silicon Small-Signal NPN Transistor

FEATURES :
- HIGH CURRENT GAIN
- FAST SWITCHING
- HIGH FREQUENCY
For further information, view it online: 2N2369 ( pdf | 2 pages)

Make Solar Cells Using Transistor 2N3055

It's easy to cut open a power transistor like the 2N3055 to expose the NPN silicon material inside to make a solar cell. When exposed to sunlight, or household lights, it conducts electricity. The N-type and P-type materials work like a solar cell. The best way is from the Base to the Collector though from both the Base and Emitter combined and then to the Collector also works well. The voltage and current aren't much but with just a few of them in series you can power a small 1.5 volt calculator.

2N3055: Silicon High-Power Transistor

....PowerBase(TM) complementary transistors designed for high power audio, stepping motor and other linear applications. These devices can also be used in power switching circuits such as relay or solenoid drivers, dc-to-dc converters, inverters, or for inductive loads requiring higher safe operating area than the 2N3055 and MJ2955.

For further information please view it online: 2N3055 (pdf | 8 pages)

2N7000: N-Channel Enhancement Mode Field Effect Transistor

FEATURES :

• Efficient high density cell design approaching (3 million/in2)
• Voltage  controlled small  signal  switch 
• Rugged
• High saturation current
• Low RDS  (ON)

For further information please view it online: 2N7000 (pdf | 10 pages)

2N2222: NPN Switching Transistor

FEATURES :

• High current (max.800mA)
• Low voltage (max. 40V)

APPLICATION :

• Linear amplification and switching.

DESCRIPTION :

• NPN switching transistor in a TO-18 metal package.
• PNP complement : 2N2907A.

For further information, view it online: 2N2222 (pdf | 8 pages)