Posts Tagged ‘2N3904’

Transistor regulator circuit can adjustable output voltage

This circuit is maintain a constant voltage, the output voltage is adjustable.Serves to reduce the input voltage, and keep the voltage constant.
The Q1 2N3904 is the amplifier model. common-emitter. This causes the voltage across the collector’s pin with the ground.Is equal to the voltage between the legs to the ground base of Q1. The volt base-emitter (0.6 V), the zener diode volt (6.2 V), then adjust the voltage VR1.
This circuit has a temperature coefficient is very little, almost zero. The joint base – emitter of Q1 with a temperature coefficient of -2 mV per Degree Celsius And zener didoe ZD1 have the temperature coefficient of +2 mV per degree Celsius. Reduce the effect of temperature on the circuit.
The Q2 to drive the output up. However, the output voltage drops, which can be adjusted with VR1 voltage range 6.8 – 15.6V. The R3 and C1 act as RC filters, voltage ripple less.But this circuit is less than 100 mA current only, is ideal for low current circuits.

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Low volt LED Flasher

In the circuit diagram for the Joule Thief, the common point of the toroid is the connection at the top of the hand-wound ferrite toroid, in the upper right of the diagram. This goes to the positive end of the battery. The other two wires from the toroid go to the resistor and to the intersection of the transistor with the LED.
One other detail that you may need to know is the symbol and pinout of the 2N3904 transistor. In the symbol, the part with the arrow is the “emitter”, the “collector” is the end above it, that also connects to the LED, and the “base” is the wire leading off to the left, between the collector and emitter. (Also remember that the end of the LED with the flat side and short lead is the end that has the flat bar in the diagram.)

Read More Source: http://www.evilmadscientist.com/article.php/joulethief
Thank you.

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TV Transmitter by 2N3904

This circuit from Poptronix allows you to send video to any television in the house. It’s as educational as it is practical. Since it’s from Poptronix, a circuit board layout is included….

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Read More Source:

http://web-ee.com/images/TVTransmitb.pdf

Thank you