Re: Pease tuneable MFB band-pass filter
On Sun, May 11, 2025 at 04:21 PM, John Woodgate wrote:
I have uploaded the above as a .ZIP. According to Bob Pease, the gain at the peak should be close to 34 dB, independent of the tuned frequency.
Then he must hav ereferred to a different circuit, maybe one with two variable elements, as used in the George Massenburg parametric EQ.
I don't get either of those results using version 24.1.8.
Neither do I.
However, the bandwidth is fairly constant with frequency, as predicted.
That's not what I see. I see the BW narrowing a
I can't believe Bob Pease reported the performance in error.
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Re: Pease tuneable MFB band-pass filter
The bandwidth is constant, so the Q varies
with frequency. I agree that the tuning range is restricted if
R2 isn't varied over a very wide range, because the peak
frequency is proportional to sqrt(R2).
It is interesting to regard it as a bridged-T.
On 2025-05-11 16:24, Jerry Lee Marcel
via groups.io wrote:
This circuit is basically an inverter with a bridged-T in the
feedback. Since it has only one variable element, the amplitude
of the peak and the BW (some say "Q") vary. Its usage is usually
reserved for applications where the tuning range is restricted.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
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Re: Pease tuneable MFB band-pass filter
Gain being dependent only on the ratio of R3/R1 would depend on having enough gain-bandwidth in the opamp.
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Re: Pease tuneable MFB band-pass filter
Ah, yes. I have that book and see that circuit. You must be referring to the circuit described starting on page 236 entitled "Multiple Feedback Bandpass Filter". Excellent. Thank you very much.
Thank you.
I would d "have, but I downloaded the article
that triggered my interest it from Electronics Design News some
months ago, and I can't now find it in the EDN articles. In the
article is a reference to page 236 of 'Analog Circuits - World
Class Designs', edited by BP, but this doesn't address varying
R2 over a wide range of tuning. However, it does say that
varying R2 doesn't change the peak frequency gain, and that gain
is R3/2R1.
On 2025-05-11 15:27, Dave Daniel via
wrote:
Would you please supply the original article,
chapter or whatever in which Bob Pease wrote his result? Thank
you.
I have uploaded the above as a .ZIP.
According to Bob Pease, the gain at the peak should be
close to 34 dB, independent of the tuned frequency. I
don't get either of those results using version
24.1.8. However, the bandwidth is fairly constant with
frequency, as predicted. I can't believe Bob Pease
reported the performance in error.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own
Opinions Only
If something is true: * as far as we know - it's science
*for certain - it's mathematics *unquestionably - it's
religion
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
|
Re: Pease tuneable MFB band-pass filter
John,
The article is listed here.
.
NOTE: THE ARTICLE HAS THE TITLE WRONG.
It is a bandpass circuit.
Mike
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Re: Pease tuneable MFB band-pass filter
John,
Your schematic has the net "OUT" connected to the junction of R2 and C2.
Move "OUT" to the output pin of U1.
Mike
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Re: Pease tuneable MFB band-pass filter
This circuit is basically an inverter with a bridged-T in the feedback. Since it has only one variable element, the amplitude of the peak and the BW (some say "Q") vary. Its usage is usually reserved for applications where the tuning range is restricted.
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Re: Pease tuneable MFB band-pass filter
I would have, but I downloaded the article
that triggered my interest it from Electronics Design News some
months ago, and I can't now find it in the EDN articles. In the
article is a reference to page 236 of 'Analog Circuits - World
Class Designs', edited by BP, but this doesn't address varying
R2 over a wide range of tuning. However, it does say that
varying R2 doesn't change the peak frequency gain, and that gain
is R3/2R1.
On 2025-05-11 15:27, Dave Daniel via
groups.io wrote:
Would you please supply the original article,
chapter or whatever in which Bob Pease wrote his result? Thank
you.
I have uploaded the above as a .ZIP.
According to Bob Pease, the gain at the peak should be
close to 34 dB, independent of the tuned frequency. I
don't get either of those results using version
24.1.8. However, the bandwidth is fairly constant with
frequency, as predicted. I can't believe Bob Pease
reported the performance in error.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own
Opinions Only
If something is true: * as far as we know - it's science
*for certain - it's mathematics *unquestionably - it's
religion
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
|
Re: Pease tuneable MFB band-pass filter
Would you please supply the original article, chapter or whatever in which Bob Pease wrote his result? Thank you.
I have uploaded the above as a .ZIP. According
to Bob Pease, the gain at the peak should be close to 34 dB,
independent of the tuned frequency. I don't get either of those
results using version 24.1.8. However, the bandwidth is fairly
constant with frequency, as predicted. I can't believe Bob Pease
reported the performance in error.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
|
Pease tuneable MFB band-pass filter
I have uploaded the above as a .ZIP. According
to Bob Pease, the gain at the peak should be close to 34 dB,
independent of the tuned frequency. I don't get either of those
results using version 24.1.8. However, the bandwidth is fairly
constant with frequency, as predicted. I can't believe Bob Pease
reported the performance in error.
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
|
Re: Crystal oscillator oscillation startup
@Andy
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> I rarely ever see cases where a crystal needs to be modeled in SPICE as more than two resonant circuits (series and parallel), and one is usually sufficient.
In this case, shall I use the or ?
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Re: IP3 or 3rd Order Intercept Point Plotting
Hi Dan, IMD testing in RF can be done with two tone testing and looking at the spectrum of the output or you can use a single input, step its value and plot gain against the power out. In a well behaved amplifier the gain will drop 1dB when non linearity starts to arrive. There is a rule of thumb that OIP3 is12-14dB above the P(-1dB) point. Radio hams would use the ARRL or RSGB handbook to read up on this. Designers of amateur radio circuits would use the book Experimental Methods of RF design, affectionately known as EMRFD. Out of print but really useful.?
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For two tone testing you could look at a file in the archive; Two_Tone_OIP3_EMRFD_fig2-57_ATC.zip and get some useful background.
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Apply two voltage sources in series, give each an internal impedance (Rser) of 25 Ohms, ensure your amplifier has a 50 Ohm load on its output. You need to run a .TRAN analysis of course to see non-linear effects.
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The three settings of the .TRAN command are critical to allow use of the FFT command. The start and stop times MUST start and end near zero, the maximum timestep has to be kept very small. Look at the voltage out after simulation and zoom right in to the stop and start of the waveform. It may help to use two tones (frequencies) that make this easier, I use 14 and 14.2MHz (in real life my two tone oscillator has a separation of only 20kHz, but it doesn't seem to matter)
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The theory of two tone testing is that if you apply 14MHz (f1) and 14.2MHz(f2) you will see and putput spectrum with these two tones, and also tones at 13.8 and 14.4MHz (and a smorgsbord of frequencies of multiplies of each tone added or subtracted from multiplies of the other tones) The 13.8 and 14.4 tones are twice f2 less f1 and twice f1 less f2. If you record the amplitude of one of the fundamental tones and one of the intermodulation products you can get the OIP3 by adding half the difference to the amplitude of the main tone. You must correct for the fact that the FFT uses dBv by adding 13 to get dBm.
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It's a pity you can't use .MEAS on fft waveform results but instead you can use .MEAS commands to plow through the .RAW simulation results and extract the amplitude of one tone. The sequence of 4 or 5 commands to do this are in Tony's example.
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It took me a while to understand how these worked, you can think of it as realizing that you can measure DC (zero Hertz) by averaging and that "mixing" a desired frequency to zero hertz allows you to measure the desired frequency, with the added complication you don't know the phase of the desired f so you have to use quadrature waveforms and combine the results.
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I hope that all helps, the forum here is about LTspice and not circuit design but hopefully you find the above useful. I sometimes wish the forum had better "examples of good practice" and more tutorial related examples, rather than being full of people's problems.
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I am a radioi amateur in the UK, my callsign is MI5AFL, (I am listed in QRZ if you are a member of the tribe of amateurs)
Regards
Ian McCrum
MI5AFL
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Re: Single-phase H-bridge inverter circuit
Hi Andy,
Thank you so much for your explanation. It was very helpful!
I just have one more question (I hope I¡¯m not bothering you): in our example, the power supply voltage is 5V. But what if our power supply is much higher, say around 300V? The MOSFET needs a gate-to-source voltage (Vgs) that is higher than the source (Vs) to turn on. So, if we keep using a 10V PWM signal referenced to ground, it wouldn¡¯t work properly.
I¡¯ve been researching this, and I came across the bootstrap driver technique. Is this commonly used in such high-voltage applications? Or is there another configuration we should use in this scenario?
Thanks again for your help!
By the way, do you have LinkedIn? I really appreciate your knowledge of LTspice. Congratulations!
Guilherme
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Re: IP3 or 3rd Order Intercept Point Plotting
On Sat, May 10, 2025 at 12:36 PM, John Woodgate wrote:
No John.?
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Just one of likely numerous ways.?
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Re: IP3 or 3rd Order Intercept Point Plotting
Is it on a stone tablet?
On 2025-05-10 20:17, alan victor via
groups.io wrote:
On Sat, May 10, 2025 at 06:16 AM, Dan wrote:
Are there any files, messages etc, that detail how
to plot the IP3 of an rf amplifier using LTspice?? I would be
interested in comments and examples on this subject.
This gentleman does a nice review of your query. See page
starting at 16...?
?
?
--
Best wishes John Woodgate RAYLEIGH Essex OOO-Own Opinions Only
If something is true: * as far as we know - it's science *for
certain - it's mathematics *unquestionably - it's religion
|
Re: IP3 or 3rd Order Intercept Point Plotting
On Sat, May 10, 2025 at 06:16 AM, Dan wrote:
Are there any files, messages etc, that detail how to plot the IP3 of an rf amplifier using LTspice?? I would be interested in comments and examples on this subject.
This gentleman does a nice review of your query. See page starting at 16...?
?
?https://www.gunthard-kraus.de/LTSwitcherCAD/SwitcherCAD-Tutorial_English/pdf-File/RF_English_01_final.pdf
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Re: Access .model parameters by name in expressions
I think such a feature would be very useful.
I've made a feature request to ADI.
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Re: Latest syntax checking improvement and related issues
Tony thanks, I've downgraded to 24.0.9 I've found on my disk.
The Bordodynov lib (I've been using various exotic parts from) needs a deep cleanup with the latest, otherwise it does not allow to start simulation (at least here). .
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Re: IP3 or 3rd Order Intercept Point Plotting
On Sat, May 10, 2025 at 09:16 AM, Dan wrote:
Are there any files, messages etc, that detail how to plot the IP3 of an rf amplifier using LTspice?
Plain old common sense (which might not be correct) suggests that you would want to use a .FOUR command to extract the amplitudes, and then use it with time-domain (.TRAN) simulations where you .STEP the amplitude.? Have you thought about doing that?
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How would you do it if you had the device on a lab bench?? What equipment would you use and how would you set it up and measure it?? Maybe you would do the same thing in LTspice.
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For RF circuits, obtaining good models is often the most difficult part.
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Andy
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On Fri, May 9, 2025 at 05:18 PM, <arhamishtiaq42@...> wrote:
Also i want to make the PCB of this circuit in KICAD software if you have any idea how can i design this transformer do i have to place the ADuM3190-chip in my pcb??
Note that LTspice can export (convert) the schematic into netlist files for a variety of CAD programs.? In the schematic viewer, go to Tools > Export Netlist, and read the Help page for Schematic Capture > PCB Netlist Extraction.? KiCad is not one of the listed file formats, but I am assuming it can open at least one of the listed file types.
Accel, Algorex, Allegro, Applicon Bravo, Applicon Leap, Cadnetix, Calay, Calay90, CBDS, Computervision, EE Designer, ExpressPCB, Intergraph, Mentor, Multiwire, PADS, Scicards, Tango, Telesis, Vectron, and Wire List
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About the transformer and ADuM3190, if you plan to use them in your design, then I think it only makes sense to put them on your PCB.? Otherwise, they would need to float in space with wires going to the PCB.? If you don't plan to use the ADuM3190 then it does not need to be there, of course.? It was there for a reason, but you might not need that reason.? It's up to you.? If I remember correctly, Udo's schematic had two transformers, one purchased and the other hand-made (or maybe manufactured according to your specifications).
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Andy
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John Woodgate
Roy McCammon
Ian McCrum MI5AFL