Datasheet BC548 Philips
http://www.hebertech.com/view/1850-philips-bc548.pdf
 
 

15V Dual Power Supply For Preamplifiers
This is 15v dual power supply for preamplifiers, which it can provide output +15V/-15V regulator using transistors and zener diode, so easy to find parts and build easily it.
https://www.eleccircuit.com/dual-dc-regulator-15v-using-c1061-and-a761/

5 channel graphic equalizer by BC548 transistor
The equalizer circuit can adjust the frequency to 5 channel is 60 Hz, 100 Hz, 1 kHz, 3 kHz and 12 kHz.
If the system is used in stereo, then build up to another set.
http://www.eleccircuit.com/5-channel-graphic-equalizer-by-bc548-transistor/

Binaural Receiver for 40 Meters by WB8ICN
Actually it started out wanting to play with a ceramic resonator oscillator and this receiver had one. So I built the oscillator first…it worked first time and I am quite happy with the results thus far.
https://wb8icn.wordpress.com/2014/05/05/binaural-receiver-for-40-meters/

Binaural Receiver Update by WB8ICN
Swapped out the experimental variable cap I was using for tuning and installed a salvaged 27 to 267pf variable cap. Also made some voltage measurements for my data book.
https://wb8icn.wordpress.com/2014/05/07/binaural-receiver-update/

Elektrische kaars
Om een kaars te laten branden, hebben we een verhittingsbron nodig (het vuur van een lucifer) en om hem te doven hoef je hem slechts uit te blazen. De volgende schakeling gedraagt zich op overeenkomstige wijze.
http://www.circuitsonline.net/schakelingen/98/lichteffecten/elektrische-kaars.html

Lie detector circuit
This is a false capture circuit or Lie detector circuit. The basic principle of the resistance of human skin. While dry skin is a resistance of about 1 Mega ohm but if the skin moisture resistance is reduced. When the body are excited or scared or not sure the skin is moist than usual.
http://www.eleccircuit.com/lie-detector-circuit/

Pre amplifier with transistors BC548
Pre amplifier circuit with transistors can be used to supply source from 6-12Volt the current minimum is 2-3 mA and can extend the signal strength from up to 2 Volt.
http://www.eleccircuit.com/simple-preamplifier-circuits-by-transistors/

Signal Frequency Beat Frequency Oscillator by VK3YE
The days when you could listen to amateurs on a simple shortwave AM receiver are with us again, thanks to the development of this one-transistor, frequency-agile signal frequency beat frequency oscillator.
http://home.alphalink.com.au/~parkerp/projects/projbfo.htm

Simple flashing light by transistor BC548
WIDTH="96" HEIGHT="72"This circuit basically the base of LED Flashing circuit, the character generally be have Transistor stay 2 work alternate be be like the automatic switch that alternate work.WIDTH="96" HEIGHT="72"
http://www.eleccircuit.com/dual-led-flasher-by-2n2907/

Small FM radio receiver
WIDTH="96" HEIGHT="72"This circuit is FM radio receiver that very small size and works well, although the sensitivity is poor. The principle of this circuit is to use the generator frequency circuit.WIDTH="96" HEIGHT="72"
http://www.eleccircuit.com/small-fm-radio-receiver/
 

The Op-amp IC tester circuit
This is an simple op-amp IC tester circuit that cheap and easy to build. for test many op-amp ICs fast check.
http://www.eleccircuit.com/the-op-amp-ic-tester-circuit/