Video Switching

[premkumar9]

Hi,
I need to switch either one of two composite video inputs to a single output. Plan to use a PCB mounting relay. Can anybody suggest a better solution using solid state devices.

 

[Nigel Goodwin]

Depends what you mean by 'better', a relay works absolutely perfectly, any electronic solution is far more complicated, and lower quality.

 

[premkumar9]

Depends what you mean by 'better', a relay works absolutely perfectly, any electronic solution is far more complicated, and lower quality.

Better considering cost, signal quality and reliability.

 

[Nigel Goodwin]

A relay is probably better on all three.

 

[blueroomelectronics]

Cheap too. Use a SR relay and it'll draw zero current once switched.

 

[premkumar9]

A relay is probably better on all three.

Can I drive many relays (switching ON simultaneously) using single transistor and flywheeling diode OR separate transistors required for each relay?

 

[premkumar9]

Cheap too. Use a SR relay and it'll draw zero current once switched.

What is that relay? Your site is still down?

 

[Roff]

Depends what you mean by 'better', a relay works absolutely perfectly, any electronic solution is far more complicated, and lower quality.

Relays have perfect differential gain and phase, low crosstalk, and low noise. However, if you want to switch between synchronous sources and not see the switch on the TV screen, relays suck. Our OP hasn't said what his application is. If it's just for home use, relays should be fine.

 

[Nigel Goodwin]

Can I drive many relays (switching ON simultaneously) using single transistor and flywheeling diode OR separate transistors required for each relay?

Yes you can.

 

[premkumar9]

Increasing output

I have one more doubt. I attach audio and video distribution amplifier circuits for driving three 75 Ω load. Can I increase it to 10 with the same circuit configuration by changing the componentss to higher rating? I

 

[Roff]

Have a look at Linear Technology's LT1206 and LT1207. These parts are challenging to use, but strict adherence to the datasheet regarding feedback resistor values, power dissipation, heatsinking, supply decoupling, etc., will pay off. You should be able to drive ten 150 ohm loads with either part.

 

[premkumar9]

Have a look at Linear Technology's LT1206 and LT1207. These parts are challenging to use, but strict adherence to the datasheet regarding feedback resistor values, power dissipation, heatsinking, supply decoupling, etc., will pay off. You should be able to drive ten 150 ohm loads with either part.

May be possible to make the required amplifier with those ICs. But in my case due to some reasons I wanted to know whether 10 O/P can be driven by changing the output transistors. if so, wanted to locate transistors which give satisfactory result with out affecting band width. Of course I can experiment and find out. But wanted an expert opinion for saving time and effort.

 

[Roff]

May be possible to make the required amplifier with those ICs. But in my case due to some reasons I wanted to know whether 10 O/P can be driven by changing the output transistors. if so, wanted to locate transistors which give satisfactory result with out affecting band width. Of course I can experiment and find out. But wanted an expert opinion for saving time and effort.

It would be difficult for me to predict without breadboarding or at least simulating with different transistors. The ones specified are already pretty substantial. Higher power transistors in general have higher capacitance and lower Ft, both of which are detrimental to bandwidth.