ADL5330: Single ended inputs and outputs

Document created by analog-archivist Employee on Feb 23, 2016
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I am using your ADL5330 RF VGA in a broadband single-ended application of
100MHz to 2GHz. Therefore, I think that the balun approach is not viable. The
datasheet says that it is possible to simply tie the INLO input to ground via
the decoupling cap - would I simply use a series 25ohm resistor to give a 50ohm
input-impedance to the VGA? The datasheet also says that a balun MUST be used
on the outputs - this appears to counter the broadband advantage of a purely
resistive input! Won't the output balun limit the output bandwidth capability?
What is the bandwidth of the ADL5330 Eval-Board? It doesn't appear to say in
the datasheet.

 

The input of ADL5330 can be driven single ended by simply grounding the unused
pin and driving the input terminal by a 50ohm source. DC blocking capacitors of
100pF are required as shown in figure 34 in the datasheet. However for optimal
performance the input baluns are recommended

The output of the ADL5330 is differential and it is suggested to use a 1:1
balun to convert to single ended. However if the customer wants to use a single
output, proper care has to be taken to provide the right bias to the unused pin
and adequate ac load.     

We suggest the customer use ETC1-1-13 balun from MA-COM for broad band
operations wherever the balun is necessary. It is rated for 4.5MHz to 3000MHz.
The insertion loss increases at higher frequencies though. If loss is of
concern, narrow band baluns are recommended. Please see the attached datasheet
for the ETC1-1-13

Having a fully differential signal path reduces common mode noise, it reduces
the susceptibility to common mode interference with other circuits. It has
other benefits such as reduced parasitic feed through as the return path for
differential circuits are well defined.

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