Connecting two RF amplifiers together

[MichailM]

I have a 36dB, 50kHz to 1.5GHz coaxial (SMA) RF amplifier which I use to amplify pulse signals (double exponential of rise time 2-3ns and duration ~20ns). What will happen if I connect two 36dB amplifiers one after another? So, the coaxial out of the amp 1 will be the coaxial in of amp 2. Pretty much I need to amplify my signal more than 36dB and I was wondering if such an option would be functional...

Thanks!

 

[barry]

you need to check input levels. Will the output of the first amp overdrive the input of the second?

 

[danadakk]

Amplifier part number ?

Generally speaking, short answer is NO if they develop appreciable power.


Regards, Dana.

 

[BigBoss]

72dB Power Gain is too much. Avoid to connect them in cascade.
As said, the second amplifier will either be hard saturation and it won't amplify or they will oscillate.
Not practical..

 

[MichailM]

Amplifier part number ?

Generally speaking, short answer is NO if they develop appreciable power.


Regards, Dana.

It is a C5594 from Hamamatsu used to amplify the output of a PMT. To be honest I don't know how much power is considered too much. The PMTs do not generate currents greater than 100uA so with a 50Ohms load resistance so around 5mW.

 

[danadakk]

There is no spec on the allowed input range, I would contact Hamamatsu to establish that.

Secondly you have the BW shrinkage factor that will apply to cascade of stages, not sure if
that matters to you.

Note the calculation a little more complex as your response is bandpass, whereas
the above derivation based on LPF. But you get the idea. Shrinakge factor then woukld
be ~ .64


Regards, Dana.

 

[FvM]

According to Hamamatsu datasheetthe amplifier is suitable for single phonto counting with PMT. Respectively the gain should be sufficient for typical applications with correct PMT voltage.

Besides possible oscillation issues with cascaded amplifiers, you should be aware that amplified input noise will already use a considerable share of the available signal swing at the second amplifier output. If you want a bit more gain than 36 dB, e.g. 40 to 50 dB and don't have a suitable amlifier then you should consider 25 to 30 dB attenuation between both amplifiers.

What do you exactly want to achieve?

 

[MichailM]

My apologies for coming back late. Thank you all for your replies. The attenuator option FvM suggested sounds very interesting I will give it a try very soon and I will come back with an update. I could possibly check the BW of the entire set-up with a VNA and correlate with the suggestion of danadakk