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When you use a transformer with the push pull configuration like
Q93, Q97. the collector sits quiescent at the supply voltage. Then
you add the + signal swing on to that to get the maximum voltage
the device sees. So with a +2 V supply, you can't go lower then 0
volts, so you can't go higher then 2+2= 4 volts. That leaves a 1/2
volt margin for derating the device.
On 6/9/2018 11:54 AM, Jerry Gaffke via Groups.Io wrote:
Thanks for posting that!
I find it interesting that you got away without a transformer at
You say flat to 30mhz, have you breadboarded it, or is that a
result from simulation?
Those parts are likely a bit too expensive for hfsignals, but way
more cost effective for most of us
than spending weeks trying to get some $0.15 parts to do the job.
> The MMIC has a absolute maximum voltage of 4.5 VDC.
> Assuming you use a transformer (actually you must to get the
drive level you need for the output stage)
> you an only use a +2 volt supply for the device for a 4 v
Mouser summary for the BGA616 mmic says a 6v supply, but turns out
that's the rail
feeding the resistor, the device sees 4.5v max.
Most of the new devices are shooting for very low power supply
I can't quite follow the logic regarding the statement "you can
only use a +2 volt supply".
With a transformer between the mmic and the load it would seem the
mmic supply could be most anything.
Data sheet suggests it would typically be a 33 ohm resistor from
6v, device drawing 60ma,
so 6v - 33*0.060 = 4.0v at the device if trying to use the BGA616
At 18dBm, that mmic might just barely replace Q911,912.
But not drive the IRF510's.
Not a good choice for inclusion in the uBitx.
But still, an interesting and very cheap mmic.
On Sat, Jun 9, 2018 at 06:00 am, Howard Fidel wrote:
Attached is my driver it goes between VR1 and the
outputs of T10 you need to remove C84 and T10 and insert this
circuit. I am using the AMP signal to reduce the overall power
output when driving a linear amp which needs 5W not 10W. U7 is a
current driver, I chose it because I have a number of them, I
probably could select something better, or use an emitter
follower but it should do the job at 0 cost for me. The same
with the T13-1 transformer, I have them. The opamp was selected
for its speed slew rate voltage and current drive capability.
C45 is there because U7 needs a minimum load capacitance for
stability. I will see if I need to add something there later. TX
is the switched 12 volts that is there in transmit only.
I am working on a PCB with this being one part of a daughter
board for the uBitx. I would be interested in any feedback. I am
not suggesting that this is a cost effective way of improving
the uBitx for production. I will post the entire schematic in a