Distribution of Video to various recorder or TVs without losses or distortion is quite difficult.
During the distribution of the video some losses and distortion might occur to decrease the quality of the video , but don’t worry here is a simple electronics project to overcome the problem , This video distribution amplifier enables four video recorder or TVs to be connected to the output of one VCR or VCP. The circuit “Video Distribution Amplifier” can be used as distribution amplifier not only for VCR or VCP but also for all other signal having a bandwidth of about 10 MHz.
The circuit of video distribution amplifier utilizes popular IC 733 (IC1) which is a simple single-chip amplifier. This IC can be used to amplify the signal with a bandwidth up to 20 MHz. Here in this circuit, it is used only for up to 10 MHz because video bandwidth is about 5 MHz max. The gain provided by this IC is five times which should be more than sufficient to compensate for cable losses and loading losses.
The input video signal is given to the video distribution circuit through filter circuit made from two parallel capacitors as shown in circuit diagram. Variable resistor VR1 allows to set the amplification to some extent and given to the input of IC1. The output of IC1 from pin 7 is given to buffer amplifier made from transistor T1 and T2. Transistor T2 serves as a current source for T1. The heat sinks are used for both transistor T1 and T2 because their working current is set to 100 mA. The resistor networks at the output serve as impedance matching networks if long coaxial cables are used.
The power supply for the system is very straightforward and simple. The mains AC supply is stepped down by transformer X1. The output of the secondary transformer is rectified by a bridge rectifier comprising diodes D3 through D6 and filtered by capacitors C21 and C22. The regulated +5V and -5V from regulators 7805 (IC2) and 7905 (IC3) powers the entire circuit.
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1 = 470 Ω
R2 = 10 KΩ
R3, R4 = 1 KΩ
R5 = 330 Ω
R6 – R13 = 150 Ω
R14 = 6.8 Ω
VR1 = 1 KΩ
|C1, C4, C5, C7, C11, C13, C15, C17 – C20 = 0.1 µF
C2, C8 = 100 µF/16V
C3, C9 = 10 µF/16V
C6 = 220 µF/16V
C10, C12, C14, C16 = 470 µF/16V
C21, C22 = 2200 µF/25V
|IC1 = 733 (metal can package)
IC2 = 7805
IC3 = 7905
T1, T2 = BD139
D1, D2 = 1N4148
D3 – D6 = 1N4002
|X1 = 230V AC primary to 9V – 0 – 9V AC 200mA secondary transformer2 Heat sinks|