Video amplifier splitter using transistor

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 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.


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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.

This circuit requires enough power supply. Do you have this one? If you do not have it. Look:A lot of Power supply circuit

Keep reading: ‘Simple video amplifier circuit’ »

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alejandro

Perfect! i start to build it. And i need to distribute LEFT and RIGHT audio channels too.

Pradip Bhattacherjee

nice url

sakura

Can this one also be use in audio?

Frank

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

Dante Klomp

Hello! Í would like the PCB for this circuit please!

ElecCircuit.com

Hi Dante Klomp,
I will send you a PCB layout via email.

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