Explanation of the 20dB VHF amplifier operation
i had made this circuit and it worked fine
http://www.electronicsforu.com/EFYLi...I-01_Aug05.pdf
i found that circuit it makes 20dB gain
http://www.electronics-lab.com/proje...009/index.html
i want to connect the FM last stage with this circuit
whats ur idea?
the second question y they work with power gain not voltage gain?
3-the o/p of my FM is 20v peak to peak i am afraid it will cause saturation so it will be distorted am i right?
This is very low output circuit.
It won't work for ur purpose.
Don't try the way u think. Better go for full tried & tested circuit available on net. Just google & u will find many. In RF matching/return loss is very important.
thank u for ur reply
what do u mean by low o/p circuit (it is 20dB gain)?
and why wouldn't it work?!
can any body help?
Amplifier may have high gain but low power output. This will be determined by the 1dB compression point of the amplifier. If you use an amplifier with a -10dBm compression point and 20dB gain it will be useless with a input of 0dBm/1mW for example as the amplifier can not provide more power than -10dBm.
The 20dB gain amplifier you refer to is basically a pre-amplifier the maximum output power that it can give is about 0.001W. It is intended for the input to a receiver, not the output of a transmitter.
Assuming the 20V you measured is across 50 ohms then your transmitter is already giving about 1Watt output. If you add a 20dB gain amplifier after this, it will have to give 100Watts.
The amplifiers performance is not just about gain it is also about a number of other requirements, output power being just one of them.
to make it simple:
Every transistor has max output level. The transistor used in ur preamp r very low power devices. Hence u get low output.
To get more power u must high power devices. If u r designing any amplifier, understand the power required by the amplifier. If ur amplifier is 60 % efficient, then to get 100 watt power u will require roughly 165w power supply.
I think u must be knowing about watts.
I hv tried to explain u in simple way.