ive designed a LNA for 0.1G to 3G, i havent added input couplign capacitor and the simulations results are just fine, the problem is when i add input coupling cap, the gain becomes negative and all the results deteriote. i wanted to know in this case can i use an external coupling capacitor which will not be considered in simulations? and also is it necessary to add coupling capacitor inthe schematic and layout. can we just ignore the coupling capacitor?