Many electronics circuits and projects for learning in simple ways.

Video amplifier splitter using transistor BD137-BC547-BC557

This is a video amplifier splitter circuit or the video splitter circuit. It is designed to take video signal is stronger and compensate for the loss of signal. Also, it is video splitter up to three outputs.

So, it is suitable for display on several television screens, or videotapes recording at the same time, too. (Now, may no a videotape.) The advantage of this circuit is inexpensive, easy, and more detail in the circuit below.

Technical specifications

  • Usually, the video amplifier circuit always has rate is a low amplifier. This circuit has the maximum gain ratio is only 4 times. Which it is different from the common pre-amplifier circuit, high gain.
  • Impedance is 75 ohms on both the input and output.
  • The bandwidth of this circuit is wide of 5 MHz.

How Video amplifier works

Video amplifier splitter using transistor BD137-BC547-BC557

The circuit contains only three transistors.

The input impedance of the circuit is determined by the value of R1. The input signal enters through C2 to the base of Q1. And, the VR1 adjusts the level of the signal swing.

The output of Q1 is connected directly to the base of Q2. The amplified gain of the circuit is determined by adjusting VR2. Which it is in the feedback circuit, between collector pin of Q2 and emitter pin of Q1.

However, the rate of gain depends on the ratio between the resistance of R5 and R6, R8, VR2, C3. The based on the used components in the circuit. We can get the gain of 1.95 to 8.7 times.

Thus, if the load is 75 ohms. The load will reduce the gain of the final amplifier section is half.  The output signal is only 1-4 times.

You can change the resistance of R9 to suit the application. For example, if only single channel networks. You use R9 is 150 ohms. But if we the second channel is used for the network. The resistor R9 should be 82 ohms, the current in the circuit will decrease.

The LM7812 is main of Dc voltage Regulator circuit in this project. I think you still to know it very well, popular IC.

Keep reading: ‘Cheapest video signal cleaner circuit’ »

The building
You can assemble all components on a perforated board. You should put carefully the device in the circuit. Points of caution are capacitors, diodes, and transistors. You put always the correct way. Otherwise, the circuit does not work and damage.

If you want the PCB layout image of this project. Please contact email to me.

The detail parts
0.25W Resistors
R1, R10, R11, R12—75 ohms
R2—10K
R3—8.2K
R4—1K
R5, R8—180 ohms
R6—3.3K
R7—470 ohms
R9—56 ohms
VR1, VR2—2.2K, Potentiometer
C2, C8, C9—0.1uF 50V_Polyester Capacitor

Electrolytic Capacitors
C1, C3—10uF 16V,
C4, C5, C6—100uF
C7—470uF 25V
D1—1N4148___ 75V 150mA Diodes
D2, D3, D4, D5—1N4001, 100V 1A Diodes
Q1—BC547b ,BC546, 45V 100mA NPN Transistor
Q2—BC557B, BC556, 45V 100mA PNP Transistor
Q3—BD137, BD139  NPN transistor
IC1—LM7812__12VDC voltage regulator IC

The setting of video amplifier circuit

When sure that the circuit is complete. Then, enter the power to the circuit to test by following method. You can adjust VR1 in two ways.

First, adjust VR1 until the voltage at the base of Q1 is equal to 1V. And there is a voltage drop across R7. (while no input signal.) approximately 0.75V.

Second, adjust VR1 in the middle, enter the input signal is 1Vp-p. Then, adjust VR2 to the lowest rate of gain.  Next, connect the TV or monitor to output. And, adjust VR1 until the test signal without distortion.

Keep reading: ‘Simple video amplifier circuit’ »

This Post Has 10 Comments

  1. Hello to every one, the contents existing at
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  3. Perfect! i start to build it. And i need to distribute LEFT and RIGHT audio channels too.

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  6. Can this one also be use in audio?

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  8. I’m a noob, I don’t understand the connection of VR2… it has 3 legs, one goes to C10 and one to R8, the third one goes to ground or is just hanging there? Thanks

  9. This site is awsome??????
    That is because all these schematics are from other peoples sites and other peoples work,whilst these are free to use for anyone the people who supply them ask if they are put on others sites to include the designers name and give the designer credit.
    This man claims them to be his own some are pasted from the original sites because they are written word perfect,but in reality when this guy tries to explain simple faults his English language is very poor.He even takes the time to copy circuit boards then puts them on here with his personal logo across them this amounts to nothing more than THEFT. Sir you are a criminal and this is why i will not put any of my work on the web,whilst i would enjoy knowing that someone else is using some of my work it would enrage me to find them on sites like this with this pratts name on them.

  10. Hello, Ray
    Thanks for your feedback. Last weekend I have many good things. I have donated blood to the hospital. You will be happy too. Yes, My English is so poor. I am trying to learn English. I hope it will improve. I do not design the circuit. I just who try it, then develop it. I saw it. I like it. It is so useful for me. I think it will be useful for friends too. I will try to rewrite and redraw clearly the circuit. I hope you will come back to visit me again.

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