Hello fellow friends
I need to make under 50mwatts FM transmitter for my uni project.All they gave us is the diagram.I have some idea about how op-amp,capacitors and resister works but when i take a look at the diagram it doesn't make any sense to me so if any1 of u please explain me where from i could begin ma project.thanks.
Nice transmitter, better than average. Looks like a commercial design for retail. Maybe the manufacturer can provide free technical support for their ripped-off circuit?
The varicap looks the correct polarity to me. Don't forget it's an RF circuit.
It is reverse-biased. Don't forget it's an RF circuit.
The 'should-be-done-this-way' example that was posted has too many extra parts and is 'not in the spirit' of a cheapest 'built down to a price' design which is one that uses the minimum of parts to do a job, with acceptable performance. These 'extra parts' do provide 'better' circuit performance (theoretcially), but on the other hand they are more circuit connections to go wrong.
Whether it's RF or not makes no difference to the DC voltage across the diode.
All right you tell me, in the original circuit, what's DC voltage across the diode? Please annotate the schematic.
Your example provided has too many extra parts and is 'not in the spirit' of a cheapest 'built down to a price' design. That is one that uses the minimum of parts to do a job, with acceptable degradation in performance.
If you let the preamp blast a very high signal then the vari-cap diode will rectify the signal and develop some bias. The audio coupling capacitor C9 might be able to hold the bias for a moment until the next audio peak.