EMRFD Message Archive 10270

Message Date From Subject
10270 2014-09-19 08:04:33 Jason Burke Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Can anyone recommend an amplifier circuit or RF MMIC IC that is capable of operation on both the VHF and UHF bands (144-148 and 420-450) and will produce at least +20 dBm of output power?  It will be amplifying an FM signal so there is no requirement for linearity.  The input signal will be on the order of +10 dBm.  Vdd is 3.3 volts and may be a limiting factor here.

I've searched MiniCircuits, Digikey, and Mouser for a suitable RF MMIC but have come up empty.  There are one or two GaAs MMICs made by Avago that might work, but they are made for operation on the 5.8 GHz band and I'm concerned there may be stability issues at VHF/UHF frequencies due to the very high gain they exhibit there.

Given the modest requirements for the amplifier, I may be better off using a discrete transistor based amplifier instead.  However, I would prefer to adapt a proven amplifier to my needs rather than to trust my limited skills in designing such an amplifier myself.  In looking through the various amateur publications I have in my library, I'm unable to find anything designed for such low voltage operation.  My next step sans any good ideas here is to get hold of schematics for an HT that operates from 3V power or less to see what they're doing.

Regards,

Jason

10271 2014-09-19 09:21:17 Clint Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Hi Jason,
 
I think you are correct – it will be difficult to find a MMIC that operates with a supply voltage of 3.3 volts.
 
I am currently building out some amps that will easily work in the range of 50 Mhz to 1 GHz, using the MCL GALI-74 and GALI-84.  These amps are available on eBay at very reasonable prices.  MCL has a minimum recommended supply voltage of 7.0 and assumes that there will be a current limiting resistor to bring the voltage at the device pin down to 5.5 volts.  The 1 DB compression point for the GALI-74 is slightly under 20 dbm.
 
The GALI-6 has similar specs, but only has about 10 db of gain.
 
MCL also has some nice packaged amps, but most of them want to see about 12 volts on the supply.
 
73
Clint
 
 
 
 
 
10272 2014-09-19 09:28:00 Clint Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
10273 2014-09-19 09:34:47 Dana Myers Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
10274 2014-09-19 09:36:15 Dana Myers Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
10275 2014-09-19 10:11:20 afu Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Hi Jason,

tell me if I am wrong...

20dBm output power at ?? 50 Ohms ??
that means a voltage ovf 2.23Vrms or 3.15Vp
which means 6.3 Vpp...............

You hope this will work with a plain MMIC ???

If you do the same game with a lower impedance ( 5 Ohms ? )
with transforming elements..... it will work

So far ...

Herbert

Am 19.09.2014 16:03, schrieb Jason Burke jasonb1963@yahoo.com [emrfd]:
 
Can anyone recommend an amplifier circuit or RF MMIC IC that is capable of operation on both the VHF and UHF bands (144-148 and 420-450) and will produce at least +20 dBm of output power?  It will be amplifying an FM signal so there is no requirement for linearity.  The input signal will be on the order of +10 dBm.  Vdd is 3.3 volts and may be a limiting factor here.

I've searched MiniCircuits, Digikey, and Mouser for a suitable RF MMIC but have come up empty.  There are one or two GaAs MMICs made by Avago that might work, but they are made for operation on the 5.8 GHz band and I'm concerned there may be stability issues at VHF/UHF frequencies due to the very high gain they exhibit there.

Given the modest requirements for the amplifier, I may be better off using a discrete transistor based amplifier instead.  However, I would prefer to adapt a proven amplifier to my needs rather than to trust my limited skills in designing such an amplifier myself.  In looking through the various amateur publications I have in my library, I'm unable to find anything designed for such low voltage operation.  My next step sans any good ideas here is to get hold of schematics for an HT that operates from 3V power or less to see what they're doing.

Regards,

Jason


10276 2014-09-19 10:50:06 David Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
You can get more output power at lower supply voltages by driving lower
impedances. Supply current will be raised but the supply power remains the same
because the voltage is lower.

So I am thinking two MMIC ICs in parallel driving 25 ohms which is then
transformed up to 50 ohms. Or maybe two MMICs in push-pull to double the output
voltage swing and a 1:1 balun to convert the doubled differential signal back
down to 50 ohms single ended.

On Fri, 19 Sep 2014 08:03:17 -0700, you wrote:

>Can anyone recommend an amplifier circuit or RF MMIC IC that is capable of operation on both the VHF and UHF bands (144-148 and 420-450) and will produce at least +20 dBm of output power? It will be amplifying an FM signal so there is no requirement for linearity. The input signal will be on the order of +10 dBm. Vdd is 3.3 volts and may be a limiting factor here.
>
>
>I've searched MiniCircuits, Digikey, and Mouser for a suitable RF MMIC but have come up empty. There are one or two GaAs MMICs made by Avago that might work, but they are made for operation on the 5.8 GHz band and I'm concerned there may be stability issues at VHF/UHF frequencies due to the very high gain they exhibit there.
>
>Given the modest requirements for the amplifier, I may be better off using a discrete transistor based amplifier instead. However, I would prefer to adapt a proven amplifier to my needs rather than to trust my limited skills in designing such an amplifier myself. In looking through the various amateur publications I have in my library, I'm unable to find anything designed for such low voltage operation. My next step sans any good ideas here is to get hold of schematics for an HT that operates from 3V power or less to see what they're doing.
>
>Regards,
>
>Jason
10277 2014-09-19 11:17:50 Jim Strohm Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Or how about an up-converting regulator?  There may not be a one-piece device to turn 3.3V into 12V, but I know that there are plenty of simple circuits out there.

73
Jim N6OTQ

10278 2014-09-19 11:34:08 John Levreault Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
For example:



Don't know your load current.

John NB1I

10279 2014-09-19 12:21:59 jasonb1963 Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Hi Clint,

Thanks for the reference.  Unfortunately, the output power of the amplifier you reference is much too low (well under 1 mW).  I did glance over other offerings at Future Electronics (their parts lookup function is grossly inferior to Digikey or Mouser unfortunately) and found some other offerings at 3.3 volts, but unfortunately none of them had a P1DB point anywhere close to +20 dBm.

Regards,

Jason

10280 2014-09-19 13:27:49 Clint Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
No problem.  Good luck on your search.  I am getting +10 dbm out on the GALi-74s with a 50 ohm load.  They will do more, but the distortion starts up and I need a clean signal from my DDS VFO.
 
73
Clint
 
10281 2014-09-19 16:51:35 jasonb1963 Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Hi Herbert,

I did run across at least one RF MMIC by Avago that has a Psat of +22 dBm at 5.8 GHz with a Vdd of 3.3 volts and 50 ohm input/output impedances (MGA-545P8).  Using the old formula:  Rout = Vcc^2 / (2*Pout) it should be possible to hit just over 100 mW with a 50 ohm output impedance.  However, when you factor in Vce maybe not.  In any event, I need a single circuit that will work both on VHF and on UHF, but not necessarily at the same time.  So I could use two different tuned networks with the same topology to achieve a 50 ohm output impedance over each band or just use a broadband transformer.  Was hoping to find a turnkey solution for this as it's somewhat out of my area of expertise.

Regards,

Jason

10282 2014-09-19 16:54:05 jasonb1963 Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Hi Jim,

Good idea, except I'm already stepping up a 1.5 volt input voltage to 3.3 volts and would prefer not to add yet another DC-DC converter stage if possible...  :)

Regards,

Jason

10283 2014-09-20 06:56:42 jasonb1963 Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Thanks to everyone for all the replies and suggestions on this.

The system I'm designing operates from a 1.5 volt battery and uses logic that operates at 3.3 volts.  Right now it looks like the best way for me to reach the RF power output target is to change the power conversion circuitry to produce 5 volts where I can actually find some MMIC amplifier modules that have the target PSAT levels, and then use a linear regulator to drop the voltage back down to the 3.3 volt level required by the logic circuitry.  It's less efficient than I'd hoped for, but I don't see any other way at the moment short of hiring a RF engineer to design the RF amplifier for me to run directly at 3.3 volts.

Regards,

Jason

10284 2014-09-20 07:35:16 radioaustralia123 Re: [emrfd] Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF
Hi,

I don’t know if this is possible,…. but. You maybe able to find a switching regulator that gives +5v out. And you maybe able to add a windings on it to give you 3.3v out. The winding could be connected out of phase to reduce the voltage at the 5V transformer tap. Or the 3.3v produced from across the added winding. You would have to find a switching regulator that allows access to the transformer and is suitable. That maybe hard fo find.  Or, maybe design your own dual output switching regulator. PC computer power supplies have multiple outputs from one switching operation. Have you also looked to see if there is an off the shelf dual output switching regulator? Don’t know what sort of power is required. But two small off the shelf switching regulators maybe the answer?

Just my two bobs worth.

Regards,

Roderick Wall, vk3yc.

10286 2014-09-20 10:56:10 David Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Using a 1:1 flyback transformer or coupled inductor with the existing 3.3 volt
boost converter may be the best way to get a higher voltage auxiliary output but
it depends on the current requirements of the two outputs:

http://www.maximintegrated.com/en/app-notes/index.mvp/id/660

On Sat, 20 Sep 2014 14:17:01 +0000, you wrote:

>Hi,
>
>I don’t know if this is possible,…. but. You maybe able to find a switching regulator that gives +5v out. And you maybe able to add a windings on it to give you 3.3v out. The winding could be connected out of phase to reduce the voltage at the 5V transformer tap. Or the 3.3v produced from across the added winding. You would have to find a switching regulator that allows access to the transformer and is suitable. That maybe hard fo find. Or, maybe design your own dual output switching regulator. PC computer power supplies have multiple outputs from one switching operation. Have you also looked to see if there is an off the shelf dual output switching regulator? Don’t know what sort of power is required. But two small off the shelf switching regulators maybe the answer?
>
>Just my two bobs worth.
>
>Regards,
>
>Roderick Wall, vk3yc.
>
>
10287 2014-09-20 20:22:39 biastee Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
Some of these MMICs can be adapted to other frequencies. For example, although the Avago MGA-30116 is recommended for a 900 MHz driver, it can be modified to work at 400-520 MHz and 220-400 MHz:
https://www.academia.edu/5482772/Mass-Market_Designed-for-Cellular_MMICs_Can_be_Gainfully_Adapted_for_Use_in_Niche_Applications_on_Different_Frequencies

The Avago MGA series are GaAs e-PHEMTs and they can operate down to 2V if you can accept some performance degradation.
http://www.microwavejournal.com/articles/1995-low-voltage-operation-of-gaas-power-amplifiers?v=preview
At 5V, 460 MHz, the MGA-30116 has a P1dB of 27 dBm. So, there is a good chance it can meet your 20 dBm requirement at 3V.


---In emrfd@yahoogroups.com, wrote :

Can anyone recommend an amplifier circuit or RF MMIC IC that is capable of operation on both the VHF and UHF bands (144-148 and 420-450) and will produce at least +20 dBm of output power? It will be amplifying an FM signal so there is no requirement for linearity. The input signal will be on the order of +10 dBm. Vdd is 3.3 volts and may be a limiting factor here.



I've searched MiniCircuits, Digikey, and Mouser for a suitable RF MMIC but have come up empty. There are one or two GaAs MMICs made by Avago that might work, but they are made for operation on the 5.8 GHz band and I'm concerned there may be stability issues at VHF/UHF frequencies due to the very high gain they exhibit there.


Given the modest requirements for the amplifier, I may be better off using a discrete transistor based amplifier instead. However, I would prefer to adapt a proven amplifier to my needs rather than to trust my limited skills in designing such an amplifier myself. In looking through the various amateur publications I have in my library, I'm unable to find anything designed for such low voltage operation. My next step sans any good ideas here is to get hold of schematics for an HT that operates from 3V power or less to see what they're doing.


Regards,


Jason
10288 2014-09-21 10:08:40 DuWayne KV4QB Re: Seeking Low Voltage Broadband Amplifier for VHF/UHF Operation
If you use 5 v you could feed the 3.3v logic through two series diodes instead of using another regulator.  I have used that several times to power 3.3 v crystal oscillators in 5 volt circuits.
73 DuWayne KV4QB