I'm needing to create a booster and the easiest schematic I've found is this: http://electronics-diy.com/500mW_FM_VHF_Transmitter_Amplifier_Booster.php however, they do not document what part they use for the amp. Does anyone know what amp they may use? Or a similarly easy way to create booster inexpensively?
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3 Answers
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The MAX2650 LNA (Low Noise Amplifier) is not the amplifier they are using, but it may be suitable, depending on the gain you want. The MAX2650 has a gain of 18.3dB at 900MHz. If you need higher gain you can cascade a couple of them.
The one in the schematic you linked to is an MMIC (Monolithic Microwave IC), like Leon says. MMICs often consist of just a couple of transistors. This is a typical MMIC package:
Notice that it has two ground pins on opposite sides for improved PCB layout, but that also means that the power supply has to share a pin with the output. The MAX2650 comes in a SOT-143 package and has separate pins for these.
answered Jul 21, 2011 at 17:51
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\$\begingroup\$ What exactly is the purpose of the link? \$\endgroup\$– EarlzCommented Jul 21, 2011 at 18:05
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\$\begingroup\$ @Earlz - Oops, my bad! :-) Fixed. \$\endgroup\$– stevenvhCommented Jul 21, 2011 at 18:12
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\$\begingroup\$ Ok much better. I'm stilling learning about how this will work and build it, but out of curiosity, do you think this would require a heatsink? My gut instinct is no, but I can't quite tell how much 320mW might be \$\endgroup\$– EarlzCommented Jul 21, 2011 at 18:28
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\$\begingroup\$ @Earlz - The MAX2650 comes in a SOT143 SMT package, so you can't mount a heatsink on it. You do want lots of copper though, for shielding, and that will also work as a heatsink. \$\endgroup\$– stevenvhCommented Jul 22, 2011 at 5:26
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As Leon says - MMIC is the name you want. Go to Digikey and search for MMIC and go from there.
For the same pinout style you could use
In stock at Digikey for $US3.44 in ones.
That's a 10 GHz part !!! You can get functionally similar ones for under $US1 with lower bandwidths.
That's known as a Micro-X 4 package.
Digikey has about 5 different parts available in 1's in stock.
Surprisingly, I find that the one I listed above is the cheapest Micro-X 4 available in 1's and in stock.
If you are willing to go to a different package, same principle otherwise, there are many more available.
Cheapest is BGU7031 from NXP. 1 GHz.
They say
1.2 Features and benefits
Internally biased
Flat gain between 40 MHz and 1 GHz
Noise figure of 4.5 dB
High linearity with an IP3O of 29 dBm
75 Ω input and output impedance
ESD protection > 2 kV Human Body Model (HBM) on all pins
1.3 Applications
Terrestrial and cable Set-Top Boxes (STB)
Silicon and “Can” tuners
Personal and Digital Video Recorders (PVR and DVR)
Home networking and in-house signal distribution
answered Jul 21, 2011 at 18:28
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It's an MMIC. At VHF virtually anything should do, such as the $1.25 MCL MAR-1+. I've constructed similar amplifiers by mounting the parts directly on a scrap of PCB material.
answered Jul 21, 2011 at 18:10
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\$\begingroup\$ Upvoted because it's you who tossed the term "MMIC", and both other answers refer to it. Still I think your answers are often a bit too brief. You don't even say what MMIC stands for, for instance. \$\endgroup\$– stevenvhCommented Jul 22, 2011 at 5:30
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\$\begingroup\$ @stevenvh, Google can easily find the definition of MMIC, so that's trivial. The answer is adequate for a specific pragmatic question for someone who is familiar with RF topics (as someone plans on building a VHF RF amplifier from a schematic should be). \$\endgroup\$– mctylrCommented Jul 30, 2011 at 3:50