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Re: Estimating Base spreading resistance for a bipolar transistor via LTspice
Hi Jerry, I am investigating a NMOSFET based class E oscillator. The BJT will be used as a driver for the mosfet and part of the feedback loop will include the rbb and the cap_be of the BJT in series
By Kamran Ahmed · #158658 ·
Re: Estimating Base spreading resistance for a bipolar transistor via LTspice
Thank you keantoken. I am interested in the Rbb at high current values. Would the s-parameters help for this estimation? If if does, then please provide some guidelines on how to do so. I am already
By Kamran Ahmed · #158657 ·
Re: 12AU7 tube heater model
IIRC, we've been told that v24.1.3? restores LTspice's ability to generate the netlist, but the netlist it generates is no longer usable as the input to new simulations Stupid.? Er, Bummer.? No, it
By Andy I · #158656 ·
Re: Estimating Base spreading resistance for a bipolar transistor via LTspice
Do you want to experiment with this in relation with noise voltage? You could probably build a theoretical model circuit of your transistor and adjust an explicit Rbb' until you have coincidence
By Jerry Lee Marcel · #158655 ·
Re: Estimating Base spreading resistance for a bipolar transistor via LTspice
I meant to say the fall in transconductance as frequency increases.
By keantoken · #158654 ·
Re: Estimating Base spreading resistance for a bipolar transistor via LTspice
For a BJT model, the parameters Rb, Rbm and Irb determine the base spreading resistance. The resistance is Rb at low currents and falls to the value of Rbm as current increases past the value of Irb.
By keantoken · #158653 ·
Re: 12AU7 tube heater model
I think it's a question that's no often asked: people just accept it as a magic number. I did a web search, which led to a URL about half a km long, so I can't post it. Instead, do a web search for
By John Woodgate · #158652 ·
Re: 12AU7 tube heater model
I haven't yet tried other than 24.1.0, but View > SPICE Netlist > Right-click > Edit as Independent Netlist > Save, is still available from the Schematic menu. I hope that feature remains, otherwise
By Tony Casey · #158651 ·
Re: 12AU7 tube heater model
Sorry, what does R^2 accuracy measure of 0.9993 actually mean ? Thanks.
By Carlo · #158650 ·
Estimating Base spreading resistance for a bipolar transistor via LTspice
Hello friends, Is there a way of estimating the base spreading resistance of a bipolar transistor by using LTspice? Perhaps via getting the transistor's S-parameters? Many thanks in advance!
By Kamran Ahmed · #158649 ·
Re: 12AU7 tube heater model
FYI - My advice about adding GMIN across current sources, is that you should specifically add them to your current sources, by adding a resistor in parallel with them. The checkbox in the Control
By Andy I · #158648 ·
Re: Build spice model of transimpedance amplifier
Keep in mind, this question was asked nearly a year ago.? This conversation ran out months ago and I don't know if the OP is still looking for answers. If I remember correctly, that person was
By Andy I · #158647 ·
Re: 12AU7 tube heater model
No, they are not the same. ".options gmin=<value>" sets GMIN to a number.? GMIN is used in a number of places in SPICE/LTspice, including in parallel with EVERY semiconductor junction.? GMIN is used
By Andy I · #158646 ·
Re: Build spice model of transimpedance amplifier
I have never been mistaken for an analog designer but if your application demands bandwidth, would considering a current feedback amplifier as the basis of your transimpedance amp be a
By aa1ww · #158645 ·
Re: 12AU7 tube heater model
Thank you Andy. Do you think .options gmin=<value> is actually the same as "Add GMIN across current sources" checkbox? In other words, does .options gmin=<value> add a <value> Siemens conductance in
By Carlo · #158644 ·
Re: using LTSPICE symbols for representation of spice netlist of OPAMP
john23, Apparently, LTspice incorrectly processes the AD797 model file.? I don't understand why it did that, but here is how to fix it. Change from this: to this: By the way, you uploaded the wrong
By Andy I · #158643 ·
12AU7 tube heater model
For tubes/valves, I always look into Radio Designer's Handbook, because the editor was a particular expert on them. Well-hidden in Figure 35.14, in the chapter on communications receivers, is a
By John Woodgate · #158642 ·
Re: Looking for advice on TRAN timing #FFT
Ryu, See the file STEP_Sine_FFT.zip that I uploaded to the Temp folder.? It shows what happens to your waveform when you .STEP the .TRAN simulation's stop time.? When the waveforms are separated
By Andy I · #158641 ·
Re: 12AU7 tube heater model
You do not need to look in the LTwiki's "undocumented" options for that.? It is standard in LTspice, in fact in all SPICE programs.? LTspice's Help is somewhat terse about it and does not show you
By Andy I · #158639 ·
Re: Build spice model of transimpedance amplifier
You could start with a current controlled voltage source. It is the H device in the list of circuit elements.
By BRUCE108 · #158638 ·