diagram ingram

The circuit diagram shows a low-cost 3-input video MUX cable driver. In this circuit, the amplifier is loaded by the sum of RF and RG of each disabled amplifier. Resistor values have been chosen to keep the total back termination at 75 Ω while maintaining a gain of 1 at the 75-Ω load. The switching time between any two channels is approximately 32 ns when both enable pins are driven. When designing a circuit board for this cable driver, care should be taken to minimize trace lengths at the inverting input. The ground plane should also be pulled away from RF and RG on both sides of the board to minimize stray capacitance. Current consumption of the cable driver is a modest 8mA.

• Overload protected
• Sshort-circuit stable
• Output current: max. 3A
• Output ripple voltage: 0.5mV
• Output voltage: adjustable from 3 to 30V, stabilized
• Input voltage: 9 to 30V AC (depending on the desired output voltage)

• Depending on the transformer used, one may chose one of two housings
• If a metal housing is used, it must be earthed for security purposes.
• Make sure the cooling body does not touch the housing. This might cause a short circuit.
• When mounting a toroidal transformer, it must be seen to that the fixation bolt does not touch the cover. This might cause the burning of the transformer
• If the circuit is to be integrated into another housing, it must be provided with ventilation holes (one may make these holes oneself), necessary for the release of the heat developed.

1. Connect a voltage meter to the points ‘GND’ and ‘+OUT’ and adjust ‘RV1’ until the desired output voltage is reached.
2. Apply some thermo-conducting pasta to the bottom side of the transistor and mount it on the heatsink.
3. If you need 3-8 volt then R2 will be 5.6K
4. If you need more than 8 volts then the R2 will be 2.2K
5. Suitable transformer 30vAC at 120VA