Power Output from an IRF510 Final Amplifier Stage is like predicted gas milage of your conventional car or for those of you who still own a Tesla -- the range of travel on a single charge. (There is still time to dump your M3.)
But 1st a short observation from the parking lot of my local Albertson's. I drive a 20-year-old car whose EOL may be rapidly approaching. While my XYL was with us, a huge part of my savings and income went to her care. I did not mind that in the least. Simply stated: It was a part of the original deal. Thus, I tuned out any thoughts of new cars and the new-fangled features. Back to the parking lot.
Opposite to me as I pulled into the parking slot was a rather large Tesla, black in color and had fully tinted windows. This car arrived at about the same time mine did. Then as if by magic the rear door opened upwards like a gull wing. It was like a symphony of motion.
The driver alighted first, a small, attractive, well-dressed Asian woman who quickly moved to the rear door opening to assist the second Asian (more mature) yet similarly appearing woman to alight from the car. It was definitely a choregraphed and rehearsed action.
Boom it came to me in a flash -- a dutiful daughter-in-law chauffeuring the mother-in-law. The gull wing door certainly eased the departure from the rear seat. A scene you don't forget concerning rank has its privileges. If it was the driver's mom, she would likely be in the front seat!
A little-known fact is that there is a significant Asian population in Newbury Park a result of the large bio-technical firm AMGEN and the location of a division of the company who builds the Si5351, Skyworks Solutions. Both operations employ this knowledge worker labor segment.
Back to the IRF510. Our IRF510 for a given set of Biasing and Drain voltage has a derived transducer gain. This is typically expressed in DB. Yesterday's post suggested my IRF510 design would produce better than 3 watts output. But any output from an IRF510 is also dependent on the input level. If we suggest a transducer gain of 10dB you ask what that looks like.
For clarity we are talking about power gain not voltage gain. So, our driver stage produced 12 Volts PTP and that comes to 360 milliwatts. If the output from the IRF510 was 3.6 watts (3600 milliwatts) then we have the following for our calculation.
Power Gain in DB = 10*log(power out/power in)
Gain = 10*log (3600/360) or 10*log (10) = 10dB.
If our transducer gain is 13 dB then the power output is 7.2 watts.
Gain = 10* log (7200/360) = 10* log (20) = 13dB.
If our transducer gain is 16dB then the power output is 14.4 watts.
Gain = 10* log (14400/360) = 10* log (40) = 16dB.
Now we can lower the water or raise the bridge, but these gain figures were based on the 360 Milliwatts of input. Transducer gains of 13 or 16dB are like 51 MPG on a Toyota Camry LE -- only achieved when the planets are aligned every 150 years. These gains are possible but NOT typical!
In my experience, 10dB of transducer gain is the more likely output. So, what is the solution and that comes in the form of more drive to the final and/or raising the Drain voltage. For those whose left hand is permanently welded to anything Bitx you will recall the Bitx40 board had the capability of supplying 24VDC to just the IRF510 for more power output.
Let's see what would happen with a 10dB transducer gain but with a 500 Milliwatt drive signal.
Gain = 10* log (5000/500) = 10* log (10) = 10dB.
To get 10dB of gain the Pout is 10 x Pin so I automatically knew the output was 5 watts. Now to see 5 watts the output across 50 Ohms has to be about 45 Volts PTP or 45^2 = 2025 and that times 2.5 = 5000 milliwatts or 5 watts.
A 13 dB transducer gain at 500 milliwatts input would be 10 watts output. That I have never seen with 13.8 VDC on the Drain.
Thus, assuming a typical 10dB transducer gain you would expect less than 4 watts of RF with 360 Milliwatts of drive.
I will try to cut a board on my CNC today since the IRF510 amp is one of my stock boards.
Them that know can make it go.
73's
Pete N6QW