power amplifer with very low Input power

Hi,i am designing a PA,Freq range 30-512MHz, supply voltage 7.5v,1.2A.Input power -5dbm(0.0316 micro watt), output power needed 5W. I am using coaxial transformers and baluns for matching. Because of very low input power i can not trigger my transistor.if i give 10dbm input everything works fine. So help me in this.How can i trigger my transistor by doing some preamplifing feedbacks adding some elements . i can not change my transistor and i have to use -5dbm input power.

You could change the class of operation of your 1st gain stage. Try Class A/B maybe? If not Class A will work.

Or add another amplifier in front of that gain stage and have it run in either Class A or A/B.

? either - 5dBm (0.3 mW) or 0.0316 μW (-45 dBm)

You need either 42 dB or 82 dB gain.

Trigger the transistor ?
I have never heard such terminology in my life ...
You have a Power Gain and you will get Output Power=Input Power x Power Gain.. that's it..
Is it a digital circuit ?