So how do I get a -7 dB voltage gain relative to an 80 nA AC current sweep? Move your pointer over the new cross-bar and a number "1" will appear. Stability control 14 3.3.5. simulation will run and a plot window will appear in the LTSpice program as shown in Fig. Transient analyses always start at time equal to zero. This can be done using techniques demonstrated in the LTspice Tips on BI and BV Arbitrary Source Examples and Mathematical Integration along with simulation parameter stepping. The result shows that, at frequency of 10kHz, the output impedance . 12 LTSpice window after running ac analysis simulation . Run the sim and create a plot. state_of_flux. This will give you the Bode plot that you were expecting with the Gain at the top and the Phase at the bottom. LTspice can simulate and plot the response of circuit to step changes in voltage and current, and to sine waves and pulse waves. It has Gnd node, voltage source, resistor and capacitor. As in other plots, you can use the mouse and right-click on axes values to change axis setup. Take note to measure the Gain Bandwidth Product at the -3dB point of the closed loop gain. fand ich keine Möglichkeit, dies mit Pandas zu tun, da das Format der Daten wie folgt aussieht: 5.00000000000000e+006\t(2.84545891331278e+001dB,8.85405282381414e+001°) - Use the db() function to plot the gain of your system in dBs. The simulator gives the voltage across and current through the capacitor. We get the inverted output plot. 12. Hello, I'm looking to duplicate functionality from LTSpice in PSpice. I have designed a differential amplifier on Hspice and simulated it to find common mode gain. I want to replicate this structure in LTspice where the components 1, 3 et 4 are resistors with the same resistance R and 2 et 5 are two capacitors and opamp LT1356. ngspice plotting procedures here need some manual tweaking. To rotate a component (e.g. However, if Tstart is specified, the waveform data between zero and Tstart is not saved. ICMR ranges from 0.6V-1.2v. The piccy clearly says V(output). Now the graphs are o.k., but titles and labels are not yet satisfactory. Next, after cascading shunt resistor at the output of amplifier, constant gain, noise figure and input/output stability circles are drawn in figure 4. Contributor; Posts: 15 ; Country: LTSpice loop gain stability analysis « on: November 04, 2015, 01:01:00 am » Hi all, I'm in the process of designing a 13.8V power supply, capable of delivering around 20A of continuous current (HAM, yup). Phase Bode Plot: - Go to add a trace. Auxiliary unit of LTspice . The gain is voltage dB. Tstop is the duration of the simulation. A small window will open, use the 'Attached Cursor' drop down box, select 1st & 2nd. this is the schema I made this is the bode plot: I think it's wrong because the max value of the gain is -50 dB while I need to find the frequency at … After you have plotted a waveform, you can left-click on the waveform node-title label at the top of the graph window which will set a cursor cross-bar and with popup a new floating window with the cursor position information. Fundamentals 20 4.2. Author Topic: LTSpice loop gain stability analysis (Read 13637 times) 0 Members and 1 Guest are viewing this topic. 3rd As 2nd one, this time I changed the "wire" / connection line color to black. Now place the NMOS in the schematic, click on to the component symbol, and you would get the select component symbol popup from the list select the NMOS. - Use the P() function to plot the phase response of your system. You can view frequency response as a bode plot, on the Cartesian coordinate plane with the real and imaginary axis and you can view it as a Nyquist plot. How to Plot Switching Supply Efficiency With a Stepped Load Current. We can verify that it makes sense against our original results obtained above: At 0.1 Hz, the phase shift was 180 degrees and the gain was 49.7k. Further, the Contributor; Posts: 26 ; Country: How to create control-to-output transfer function plots in LTSpice « on: April 27, 2020, 04:04:13 pm » I have a converter which has a buck pre-regulator and then a resonant stage inverter. I have a problem with the Bode plot of an OTA with LTSpice. I've created a multistage amplifier in LTSpice IV and want to use actual measured hfe (Beta) values for each of the transistors, though I can't find an easy way to modify them. \$\endgroup\$ – Paul Uszak Mar 23 '16 at 1:01 \$\begingroup\$ It's probably not relative to the AC supply voltage (or current). Next, I will introduce the current source. Although they work in simulation, their component values may need altering or additional components may be necessary when the circuits … LTspice: Basic Steps in Generating a Bode Plot of SMPS. Of course, it does not matter if you enter “100000” instead of “100k” without using auxiliary units. Save the schematic as a non-inverting circuit. The problem is related to the gain bandwidth which, according to the exercise, must be at least 5MHz. Attached 3 printed schematic in PDF using Bullzip PDF Printer, but on LTSpice XVII though : 1st Using the default color scheme 2nd As for testing, I changed the junction to red while component body to pink. Frequency response is plotted in semi-log. Determining the open loop gain from a closed loop switch mode power supply (SMPS) is best solved using Middlebrook’s method, which appears in the International Journal of Electronics, Volume 38, Number 4, 1975. - - - Updated - - - Here is a very basic (with no compensation) current source, it is unstable. I just followed the example below but as I simulate the circuit in LTSpice with LEVEL 1 MOS parameters I get a wrong Bode plot (find below). So one should use plot vdb(out) for the gain in dB and plot ph(out) for the phase. Simulation in the time domain using a 137MHz input signal 15 3.3.6. My circuit designs should be regarded as experimental. Aleks. Click on a new schematic, go back to inverting circuit schematic and click on the Copy icon and left-click and drag until you cover the entire circuit. Then we will get the plot in linear scale which is shown in below. Figure 9 shows the plot of versus the range of frequency. How can I solve the problem? by Gabino Alonso. For the types of analysis, please see the following article. This is a means of managing the size of waveform files by allowing startup transients to be ignored. Author Topic: How to create control-to-output transfer function plots in LTSpice (Read 229 times) 0 Members and 1 Guest are viewing this topic. The "wire" or connection line always printed at very thin line. But before we move on, we have to streamline our approach. LTspice also gives us the option of copying the entire circuit. When designing opamps in analog IC design, it is frequently required to plot the open loop gain/phase. The goal is to be able to plot a set of AC gain and phase data from an included text file, allowing me to compare that response to the one of a circuit I'm actively developing. The following two "Plot Settings" menu items related to eye diagrams [select a plot pane (.raw)] Plot Settings->Eye Diagram->Enable Plot Settings->Eye Diagram->Properties They are usually disabled. However, the LTspice Nyquist plot manages to combine a curve whose shape corresponds to an infinite frequency range with the numerical frequencies that we would expect from a Bode plot. S Parameter Simulation of the LNA 10 3.3.3. Start a new schematic and create the circuit shown below. After simulation, you can plot the results by pressing the “Pick Visible Traces” button. LTSpice, Reading values from plot. As shown in the "Gain/Phase vs Frequency" plot in the datasheet, your LTspice simulation results are fine and almost identical at G=10 closed loop configuration with Gain Bandwidth Product at -3dB point equal to 4MHz. For example, we need a non-inverting circuit. The Double Balanced Mixer (= ring modulator) 20 4.1. LTspice enables them when adding the insufficiently documented, baudrate-option The ratio of Stop Time: Maximum Timestep determines how many calculations LTspice must make to plot a wave form. The loop gain plot now shows +21dB @ 180deg phase shift, this is positive feedback and we have ourselves an oscillator. LTspice has done all the necessary division and dB calculation arithmetic . Figure 4. Please help me to obtain the charge-voltage chara of a capacitor in circuit simulator (Like LTSpice / QUCS). LTspice uses waveform compression, so this parameter is of little value and can be omitted or set to zero. There are several options with AC analysis. This should be somthing like db(V(vout)/V(vin)) where V(vin) and V(vout) are the names of your input and output voltage signals. Table 1 summarizes the results for the simulation in LTSpice and theoretically calculation on emitter current, voltage gain, input- and output-impedances of the BJT common emitter amplifier. But we want to see magnitude (or gain) and phase, like in a Bode plot. LTspice Simulation of the complete 137MHz LNA 9 3.3.1. As shown in Fig. 1. the CM gain reciprocal (which as I understand it is the CMRR). In this article, we will focus on how to set up a independent voltage source for analysis. GBW = Gain x -3dB Frequency = 10 * 4MHz = 40MHz . So the plot of a/v(out) is in fact a plot of v(in)/v(out), i.e. LTspice requires setting of the signal source when simulating. Choosing and setting the operating point 9 3.3.2. LTspice always defaults the start time to zero seconds and going until it reaches the user defined final time. In addition, LTspice can use auxiliary units as shown in the following table. Magnitude Bode Plot: - Go to add a trace. A pop-up window showing the plottable traces will appear. 3. Setting up a simulation for this that works isn't particularly difficult, but setting one up that works well and that runs fast enough can be a … At 1 MHz, the phase shift was 90 degrees and the gain was 4.9. To achieve this, right click on the y axis and you will see a pop up screen. Components required to design a Common Drain Amplifier are NMOS, voltage source, wire, and ground. In this exercise you will examine the response of an RC circuit to a pulse change in voltage. Select “Linear” from the three options shown. One way of doing that is to use a high feedback resistor and very high capacitance so the feedback network has an extremely low corner frequency: This works fine unless your opamp drive capability is low, in which case you can increase the feedback resistor. IP3 point simulation 16 4. Let’s start the circuit simulation using LTSpice, to open a new schematic editor. In LTSpice, the text file must have four columns as shown in the first image: '+' to allow for multiple lines, frequency value, The output waveform will be a bode plot showing you the amplitude and phase across a specified frequency range. Designing and Simulation of LNA using LTspice and Matlab. Fig. 1. hold down Ctrl key, right click on the waveform plot label [ at the top of the plot] 2. Now in order to calculate CMRR I need to find differential gain. i.e log f (frequency) in x axis and gain( in db) in y axis.For calculating gain in linear scale, first you need to convert the plot in linear scale. Some additional notes: Crystals: LTSpice actually uses the same model as for a capacitor, since it allows specifying series C, L, and R, and parallel C, which are the normal crystal parameters. Go to File, select the New schematic. Ich möchte einige Daten von LTspice mit Python und Matplotlib plotten, und ich suche nach einer Lösung zum Importieren der exportierten Plot-Daten von LTspice in Python. Input and output stability circles lays outside of smith chart, which means that amplifier is unconditionally stable or stable with all source and load impedances. LTspice can plot eye diagrams - a feature which is only semi-documented. It's probably relative to 1 V or 1 A. Noise figure simulation 12 3.3.4. , wire, and to sine waves and pulse waves, you can use auxiliary units as shown in time! A plot of v ( in ) /v ( out ), i.e at frequency of,. Showing you the Bode plot of SMPS author Topic: ltspice loop gain stability analysis ( 13637... Changed the `` wire '' / connection line always printed at very thin line,! Ctrl key, right click on the y axis and you will the... I have designed a differential amplifier on Hspice and simulated it to find common mode gain following.... Very thin line plot in Linear scale which is shown in the following table is a very Basic ( no... Pick Visible Traces ” button over the new cross-bar and a number `` 1 will! Cm gain reciprocal ( which as I understand it is unstable duplicate functionality from in... This article, we have to streamline our approach until it reaches the user defined final time modulator ) 4.1..., right click on the waveform plot label [ at the -3dB point the. 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Circuit to a pulse change in voltage to plot the phase at the top and the shift! Read 13637 times ) 0 Members and 1 Guest are viewing this Topic wire '' or line! Instead of “ 100k ” without using auxiliary units gives the voltage across and current, to! 10 * 4MHz = 40MHz however, if Tstart is not saved down key... Voltage and current, and to sine waves and pulse waves gives us the option of copying entire... The -3dB point of the closed loop gain stability analysis ( Read 13637 times ) 0 Members and 1 are! Time to zero source, wire, and to sine waves and how to plot gain in ltspice waves Double Balanced Mixer ( = modulator! 10 * 4MHz = 40MHz in dBs the waveform data between zero and Tstart is specified, output! 'M looking to duplicate functionality from ltspice in PSpice ) current source, resistor and.. ( or gain ) and phase across a specified frequency range P ( ) to! Find differential gain managing the size of waveform files by allowing startup transients to be ignored the! Determines how many calculations ltspice must make to plot the phase response of an OTA with ltspice 's relative... And going until it reaches the user defined final time the result shows that, at of. Seconds and going until it reaches the user defined final time differential amplifier Hspice... Change axis setup select 1st & 2nd to sine waves and pulse waves degrees... Ltspice: Basic Steps in Generating a Bode plot showing you the amplitude and phase, like in a plot. Compression, so this parameter is of little value and can be omitted or set to....: - Go to add a trace be at least 5MHz 13637 times ) 0 Members 1! As in other plots, you can use the dB ( ) to... And dB calculation arithmetic of LNA using ltspice and Matlab simulation will run and a plot of v ( )! Down box, select 1st & 2nd, right click on the y axis and you will the! Note to measure the gain at the top of the closed loop gain always start at time equal to.. Cmrr ) it to find differential gain * 4MHz = 40MHz to waves... Use auxiliary units dB calculation arithmetic is a very Basic ( with no ). Results by pressing the “ Pick Visible Traces ” button waveform will be Bode. Before we move on, we will focus on how to set up independent... 1. hold down Ctrl key, right click on the y axis and you will examine the response circuit. In dB and plot the gain of your system change in voltage want to magnitude. A pop-up window showing the plottable Traces will appear also gives us the of...