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max allowed output load

Posted: Sat Mar 17, 2018 8:21 pm
by drdieter
Hi Experts
Since January, I 'm playing with my own 14bit Red Pitaya.
I enjoy all the apps like scope or spectrum analyzer.

Now I'd like to measure my antenna by the VNA from Pavel.
First, I would simply use the bridge with 3x 50 Ohm-resistors and the antenna impedance as the 4th resistor. The signal is picked up via 1:1 transformer.

To get the references for the VNA, I have to short circiut the antenna.
Then the load for OUT1 will be 33 Ohms, (50+50)||(50+0)=33

Having no schematics available, I need to ask here:
Will I destroy the output amplifyer? What is the limit of output current allowed?

Thanks for each helping input.

Dieter

Re: max allowed output load

Posted: Tue Mar 20, 2018 7:49 am
by amike88
Take a look at this part of the documentation.

Re: max allowed output load

Posted: Tue Mar 20, 2018 9:00 am
by drdieter
Amike88,
thanks for your reply.

Unfortunately, I couldn't find the desired info in that part of the docu.
except the value of the Output Voltage of +-1V.

In between, I got info about the output amplifier used in Red Pitaya .
It should be the LT6200CS6.
Looking into the data sheet , you see that it can deliver:
Short-Circuit Current (depneding on cooling)
VS = 5V min ±60 typ ±90mA
VS = 3V min ±50 typ ±80mA

1V output at 33 ohm ~33mA.
So it seems to be not a problem.

Dieter

Re: max allowed output load

Posted: Tue Mar 20, 2018 3:32 pm
by amike88
Great that you were able to find the answer and also that it is not a problem :)