why is it typical use a single end LNA instead of differential LNA?

[liletian]

Hi Guys
What is the reason that single LNA is widely used than differential LNA? It seems that it is often a single end LNA follwowed by a differential LNA in a receiver. What is the reason for it?
Thanks

 

[kalyanasv]

Single ended are simple to implement but more importantly they do not have crossover distortion which is when the signal changes from positive to negative and for very small signals this can be pretty bad. That having said it does have 2nd harmonic distortions but these are correctable.
A Disadvantage is that single ended are not as power efficient either.

 

[goal]

usually the first stage is LNA. the RF signal from antenna is a single ended signal so LNA is single end input. the second stage of LNA is made as differential to reduce common mode noise and to cancel out even order hormonics.

 

[BigBoss]

Because inputs generally are connected with coaxial cables/connectors that are single ended structures.

 

[ltrlspree]

my understanding is that differential LNAs appear to get a better compromise in the matching network between NF/IRL.
In addition you can get 3 dbm improvement in OIP3. However, not everybody is willing to take the additional design effort to get these improvements.

 

[buckaroo]

Differential LNA is always better for common mode interference, single-ended LNA has the advantage of low current, low area, low noise figure(no balun needed).

 

[liletian]

Differential LNA is always better for common mode interference, single-ended LNA has the advantage of low current, low area, low noise figure(no balun needed).

yes, also differential LNA will have high NF than single end LNA as well