![]() ![]() (Middling products have tended to come and go very quickly on the market, to the detriment of all of us who just wanted a nice GaAsFET or whatever to play with, without having to worry about oscillation at frequencies that can burn ones' eyes out.) For more power, might as well just get a proper RF MOSFET, with a few cheap (~$10 being cheap here) types coming in TO-247 and SMT flat pack styles, good for 10s or 100s of W, and at least as many MHz, to maybe a hair over a GHz. SMTs in the same range tend to be MMICs, and bleeding-edge (30GHz+ fT?) HBTs or PHEMTs or what have you, that are probably not something you want to play with just yet. It might still be one of the best transistors, despite its metal can and boutique pricing. The next step up, honestly I'm not sure offhand if there's an SMT equivalent of 2N3866. ![]() I'd recommend MMBTH10 (or the original MPSH10 if you insist on TO-92) here, you can make a wideband amp into the low 100MHz range without too much trouble, though it won't have much power (Ic ~ 20mA tops, whatever that is, peak, into 50 ohms). are still available (at any price), and just, no one says there are better alternatives out there? Well FYI - most of those you can get a plastic PNxxxx version, or an SMT MMBTxxxx version, for a fraction of the price. Also, I don't get the metal cans if I might guess, I suppose old references are still just as available as ever? And 2N2222, 2N2369, 2N3055, 2N5179 and etc. maybe not such an oscillation hazard with only 500MHz transistors, but it doesn't help, and it will be fatal when using faster types. They're a liability both for matching to 50 ohms, and to oscillation. They give a characteristic impedance closer to 200 ohms, and relatively good coupling between each other. Likewise, at some point those long spindly legs are going to be a problem. Well, that's not even a lie, pre-matched transistors and MMICs for those bands really do have on-die matching networks. It's almost like the transmission line extends all the way up to the die. MMICs are all matched into 50 ohms or so, and get some GHz of bandwidth (several to 10s of, depending on type I suppose?). You can have a transistor with almost nil capacitance, and still limited bandwidth, just because it's running too high an impedance. Same story, you're driving a capacitance with a resistance, it can be peaked to extend a little further but if you need a lot more, you just need a lower source impedance, period. Hm, probably source impedance is getting too high as well. And I do not know what the reason is for the poor performace. As you can see, the frequency response is up to about 5.3 MHz (I know the blue trace is not perfectly constant over frequency). The source is the DDS, performing a linear frequency sweep from 1MHz to 15MHz, in steps of 100kHz each millisecond. However, it is the same as in the breadboard! Here you can see the scope output: The yellow trace is the output, the blue trace is the input. I expected full performance, as there are now no parasitic capacitors. I then built it on copper, Manhattan style (is this the correct name?). I simulated it on ltspice (adding lots of 7pf parasitic capacitors), and the simulation and reality were close to each other. The frequency response of the amplifier is bad, of course, up to about 5 MHz. Source is a DDS (AD9834), 220 ohm output impedance. I have built and simulated a schematic in LTSpice: The frequency response should be good, up to about 44 MHz: I built it on a breadboard, and tested it. It is based on a cascode amplifier, with 2N2369A. Intended for the low Megahertz range, should be broadband, moderate-low gain (for now). This would help inĭesigning the desired non-foster element for real life application.Hello, newbie here. Steppingstone towards developing the nonideal op-amp formula. Strong connection with the parameters found in the ideal op-amp formula may serve as a Although the nonideal op-amp formula has yet to be developed, the Next, an attempt to extend this formula to This formula can be used to analyse andĪccount for the differences between these topologies.įirst, the derivation of the formula using ideal op-amp with finite gain will be presented,įollowed by the verification of this formula. Topologies was developed based on observations. Were discussed and, in the process, a formula that governs the input impedance of these In this report, 2 different topologies of op-amp based NIC ![]() Ī negative impedance converter (NIC) is an active 2 port network that generates non-fosterĮlements such as negative capacitor or inductor. Final Year Project (FYP), Nanyang Technological University, Singapore. RF transistor amplifier design and analysis. RF transistor amplifier design and analysisĮngineering::Electrical and electronic engineering ![]()
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