Guys what if we use a video amplifier like this one
http://www.analog.com/static/imported-files/data_sheets/AD8010.pdf
would it to the job we are trying to do.

 

Hello,

You can also have a look at the MMIC's.
An MAV11, ERA4, ERA5 or ERA6 will work for you as 4 Vpp is about 16 dBm:
MAR and ERA.pdf

Bertus

 

Yes, Analog Devices, TI and Maxim make video amps in the bandwidths you could use. The hottest parts I know of are the MAX4444 and MAX4445.

If you use any of these parts you _must_ follow the recommended PCB layout requirements. If you don't, then the parts can oscillate in the hundreds of MHz.

I have used the MAX4444 -- and yes it did oscillate. I had too much capacitance on the output.

 

Richardo did you try it with a square wave because I wanted to know if it would work good also for square wave, it probably should because 550MHz bandwidth would imply that it can cater for the the 5th harmonic for a fundamental frequency of 100MHz. Correct me if wrong.

 

yeah i considered the fact that the mechanical strength should be retained and that the pad should be big enough to cater the component solder ... the pads are 5% bigger on all 4 sides so contact area of component and board remain the same(while reducing stray capacitance)

 

@Ronv the smd version i posted was manually routed

 

I didn't draw the ground plane on the other side of the board, but you can see the idea of a tight layout. All the "hanging parts go to the ground plane on the other side of the board.

 

so if the C6 and C7 develop impedance how're we supposed to bring it back (compensate for it)?... i mean will the impedance developed be capacitive or inductive in nature...
regarding components, they are SMD unlike last time..
Also i dont think johnny or i mentioned this before our PCB is smaller now.
It's 24.8mm by 22mm as compared to 36.6mm by 48.8mm
We took following steps to reduce stray capacities:
1-reduce trace size
Power: 0.5mm to 0.2mm
Signal: 0.76mm to 0.25mm
2-make smaller pad areas for the SMD components
3-use bottom copper power place (ground)
So after these improvements should we get better results ?
high freq. designs are tough !

Yes,you will get better results--bearing in mind RichardO's comments re pad size.

If you aren't committed to a discrete circuit,the MIMIC devices make things a lot easier.

 

Richardo did you try it with a square wave because I wanted to know if it would work good also for square wave, it probably should because 550MHz bandwidth would imply that it can cater for the the 5th harmonic for a fundamental frequency of 100MHz. Correct me if wrong.

Your reasoning sounds good to me. Just remember that you may not get full output voltage swing at the highest frequency because of slew rate limitations.

My circuit consisted of an analog multiplier, the MAX4444 and an output amp for driving 50 ohms. I don't remember the highest frequency that was applied to the circuit. I do remember that there was oscillation at around one giga Hertz! A dubious personal best.

The oscillation did not get through the MAX4444. It caused a DC offset on its output. My college found that when he touched a X10 scope probe to the input of the MAX4444 the oscillation would quit and the offset would go away.