What about FETs for Cellular Base Stations in Audio Cascode Voltage Gain Stage (line
there are many fet devices for the GHz aera. Here three URLs:
the nearest threads to this are the follow:
http://www.diyaudio.com/forums/showt...p?postid=22590 (Voltages across cascode MOSFET)
http://www.diyaudio.com/forums/showt...p?postid=23146 (folded cascode puzzle)
http://www.diyaudio.com/forums/showt...threadid=27193 (Borbely Fet Follower SPICE modeling)
http://www.diyaudio.com/forums/showt...threadid=70008 (LD1014 SPiCE models)
are there advantages by use of such fets in audio amplifier input stages?
Thank you for your comments
speed in input stages isn't a limitation in audio amplification
1/f noise can be - I doubt these devices have an advantage at audio frequencies over Si
I know GaAs MESFETs have enormous 1/f noise; the corner frequency can be round 100MHz - they are good at 1GHz up, but terrible below VHF.
I can't bring to mind data on the other types, but as rule most compound semiconductors have large amounts of 1/f noise, as there many more types of bulk and surface defect possible.
you steadily keep wasting your time.
these devices do a great job in wireless communications, but predictably won`t perform well in linear audio.
MESFETs are too noisy for good RF clock reference oscillators.
Phase noise opinion I overheard at NTMS (North Texas Microwave
Society) meeting... I have no idea what that means for audio???
I'm not entirely sure I am even repeating the rumour correctly...
He didn't specify the noise was Schottky or GaAs or GaN or SIC?
But seemed to prefer a silicon bipolar transistor up to <=4GHz...
I would have listened in more depth had I known the question
would come up again.
I think he might have said that SiGE looked promising for lower
noise??? I'm not sure now... Can't even remember exactly who
the speaker on that topic was, but I can inquire next month.
Can't even remember if I ate breakfast? Nor how to tie my shoes...
low noise with transitor is a fault
loudspeaker get 1 our 2% distostion
i don't think most important is low distotion,all design with transistor with feedback have the same characteristics .
fet bipolar and other igbt are the same with feedback.
our ear cannot listen the difference.IMHO
OTOH, High-voltage HBT would probably do quite well. Linearity is better than GaAs HEMT or LDMOS. They're quiet enough to make low phase noise oscillators with. But I don't think they're available in small periphery discretes, because the ones good for 28V are aimed at the base station transmitter market. A 10, 30 or 250W flange-mount device is a wee bit big and expensive for a diff pair or VAS.
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