BC548 NPN Datasheet and Specifications


The BC548 is a NPN bipolar junction transistor  general-purpose commonly used in designs in hobby electronics magazines where a general-purpose transistor is required.

It is low in cost and widely available.



Simple circuit of Flashing Dancing LED Light Citcuit Diagram


Simple circuit of Flashing Dancing LED Light Citcuit Diagram

This schematic shows a simple flashing dancing led circuit for multipurpose use such as decoration, signboard or aplication indicator.

The speed of LEDs can be adjusted and various dancing patterns of lights can be formed.

The circuit consists of two astable multivibrators which is one multivibrator is formed by transistors T1 and T2 while the other astable multivibrator is formed by T3 and T4. Duty cycle of each multivibrator can be varied by changing RC time constant by using potentiometers VR1 and VR2 to produce different dancing pattern of LEDs.

Flashing LED Circuit Main Component

T1 – T4 = BC548
R1 – R4 = 100ohm
R5 – R8 = 33kohm

Simple Circuit Peak Audio Level Meter Diagram


This simple schematic diagram shows how to build a circuit that will indicate peak audio response on an analogue meter, similar to a tape recorders meter.

This peak level reading audio meter circuit diagram will only work with a MOSFET type op-amp, bipolar types i.e. 741 and J-FET. The LF351 op-amps will not work in this circuit.

The circuit also has a slow decay time  and fast response time to indicate peak of the meter readings. The 1N4148 diode provides half wave rectification of the input signal, the dc output being smoothed by the 22u capacitor.

The capacitor will charge to the peak value of the input waveform, and then discharge via the meter and 18k resistor.

Simple alkaline battery charger schematic circuit


Simple alkaline battery charger schematic circuit

This simple schematic circuit was designed by Domenico Di Mario from Italy. It’s specifically designed to recharge an alkaline cells.

This circuit schematic diagram can be used with all types of alkaline cells. For AA cell it can take up to one day discharged can be recharged: it will take 1 day for a discharged AA cell or 9 V battery and up to several days for a large D type cell.

The orange LED will blink for around 5 times a second for a 1.37 V cell.

For a totally discharged cell, the blinking is faster but it will decrease until it will come to a stop when the cell is charged

To use high beta transistors such as BC337-25 or better BC337-40.