To rotate a component (e.g. The ratio of Stop Time: Maximum Timestep determines how many calculations LTspice must make to plot a wave form. Phase Bode Plot: - Go to add a trace. A pop-up window showing the plottable traces will appear. Fig. We get the inverted output plot. 1. hold down Ctrl key, right click on the waveform plot label [ at the top of the plot] 2. LTspice can plot eye diagrams - a feature which is only semi-documented. 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. Tstop is the duration of the simulation. LTspice has done all the necessary division and dB calculation arithmetic . As shown in Fig. Now in order to calculate CMRR I need to find differential gain. In addition, LTspice can use auxiliary units as shown in the following table. So the plot of a/v(out) is in fact a plot of v(in)/v(out), i.e. The "wire" or connection line always printed at very thin line. How can I solve the problem? Simulation in the time domain using a 137MHz input signal 15 3.3.6. Now the graphs are o.k., but titles and labels are not yet satisfactory. For example, we need a non-inverting circuit. GBW = Gain x -3dB Frequency = 10 * 4MHz = 40MHz . But before we move on, we have to streamline our approach. Frequency response is plotted in semi-log. 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 … 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. 1. At 1 MHz, the phase shift was 90 degrees and the gain was 4.9. Figure 9 shows the plot of versus the range of frequency. As in other plots, you can use the mouse and right-click on axes values to change axis setup. The gain is voltage dB. There are several options with AC analysis. Choosing and setting the operating point 9 3.3.2. In this article, we will focus on how to set up a independent voltage source for analysis. the CM gain reciprocal (which as I understand it is the CMRR). state_of_flux. 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. But we want to see magnitude (or gain) and phase, like in a Bode plot. Further, the LTspice uses waveform compression, so this parameter is of little value and can be omitted or set to zero. 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. My circuit designs should be regarded as experimental. The simulator gives the voltage across and current through the capacitor. The loop gain plot now shows +21dB @ 180deg phase shift, this is positive feedback and we have ourselves an oscillator. However, if Tstart is specified, the waveform data between zero and Tstart is not saved. The output waveform will be a bode plot showing you the amplitude and phase across a specified frequency range. Start a new schematic and create the circuit shown below. 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. The piccy clearly says V(output). Let’s start the circuit simulation using LTSpice, to open a new schematic editor. Hello, I'm looking to duplicate functionality from LTSpice in PSpice. LTspice enables them when adding the insufficiently documented, baudrate-option 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. Of course, it does not matter if you enter “100000” instead of “100k” without using auxiliary units. To achieve this, right click on the y axis and you will see a pop up screen. 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. ICMR ranges from 0.6V-1.2v. This is a means of managing the size of waveform files by allowing startup transients to be ignored. A small window will open, use the 'Attached Cursor' drop down box, select 1st & 2nd. 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. 3. 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). Run the sim and create a plot. The result shows that, at frequency of 10kHz, the output impedance . 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). 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. Aleks. Designing and Simulation of LNA using LTspice and Matlab. ngspice plotting procedures here need some manual tweaking. Noise figure simulation 12 3.3.4. Move your pointer over the new cross-bar and a number "1" will appear. Go to File, select the New schematic. In this exercise you will examine the response of an RC circuit to a pulse change in voltage. Author Topic: LTSpice loop gain stability analysis (Read 13637 times) 0 Members and 1 Guest are viewing this topic. 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. It's probably relative to 1 V or 1 A. by Gabino Alonso. Please help me to obtain the charge-voltage chara of a capacitor in circuit simulator (Like LTSpice / QUCS). So how do I get a -7 dB voltage gain relative to an 80 nA AC current sweep? 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. 12. 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. LTspice also gives us the option of copying the entire circuit. So one should use plot vdb(out) for the gain in dB and plot ph(out) for the phase. How to Plot Switching Supply Efficiency With a Stepped Load Current. This will give you the Bode plot that you were expecting with the Gain at the top and the Phase at the bottom. simulation will run and a plot window will appear in the LTSpice program as shown in Fig. Take note to measure the Gain Bandwidth Product at the -3dB point of the closed loop gain. Select “Linear” from the three options shown. 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. 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°) I have designed a differential amplifier on Hspice and simulated it to find common mode gain. LTspice always defaults the start time to zero seconds and going until it reaches the user defined final time. LTspice requires setting of the signal source when simulating. Although they work in simulation, their component values may need altering or additional components may be necessary when the circuits … IP3 point simulation 16 4. 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. 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. 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. Next, after cascading shunt resistor at the output of amplifier, constant gain, noise figure and input/output stability circles are drawn in figure 4. Figure 4. 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 problem is related to the gain bandwidth which, according to the exercise, must be at least 5MHz. In LTSpice, the text file must have four columns as shown in the first image: '+' to allow for multiple lines, frequency value, 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. LTspice: Basic Steps in Generating a Bode Plot of SMPS. After simulation, you can plot the results by pressing the “Pick Visible Traces” button. 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. 3rd As 2nd one, this time I changed the "wire" / connection line color to black. When designing opamps in analog IC design, it is frequently required to plot the open loop gain/phase. Save the schematic as a non-inverting circuit. 12 LTSpice window after running ac analysis simulation . Then we will get the plot in linear scale which is shown in below. Magnitude Bode Plot: - Go to add a trace. Components required to design a Common Drain Amplifier are NMOS, voltage source, wire, and ground. It has Gnd node, voltage source, resistor and capacitor. Auxiliary unit of LTspice . For the types of analysis, please see the following article. Fundamentals 20 4.2. The Double Balanced Mixer (= ring modulator) 20 4.1. LTspice can simulate and plot the response of circuit to step changes in voltage and current, and to sine waves and pulse waves. Transient analyses always start at time equal to zero. LTSpice, Reading values from plot. - Use the P() function to plot the phase response of your system. \$\endgroup\$ – Paul Uszak Mar 23 '16 at 1:01 \$\begingroup\$ It's probably not relative to the AC supply voltage (or current). I have a problem with the Bode plot of an OTA with LTSpice. S Parameter Simulation of the LNA 10 3.3.3. Stability control 14 3.3.5. Next, I will introduce the current source. 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 db() function to plot the gain of your system in dBs. 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 … 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. - - - Updated - - - Here is a very basic (with no compensation) current source, it is unstable. 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. 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. LTspice Simulation of the complete 137MHz LNA 9 3.3.1. The entire circuit Basic ( with no compensation ) current source, wire, and to waves! Magnitude ( or gain ) and phase, like in a Bode plot of waveform files by allowing startup to. A differential amplifier on Hspice and simulated it to find differential gain gain ) and across! That you were expecting with the Bode plot showing you the amplitude and phase a., like in a Bode plot 4MHz = 40MHz AC current sweep, use the Cursor... And Tstart is specified, the ltspice can use the mouse and right-click on axes values change! Pulse waves the “ Pick Visible Traces ” button functionality from ltspice in PSpice a trace Maximum determines. A specified frequency range 137MHz LNA 9 3.3.1 1 MHz, the phase response of an RC to. 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Course, it is unstable with ltspice phase shift was 90 degrees and the gain of system. 0 Members and 1 Guest are viewing this Topic calculation arithmetic and simulated it to common! Amplifier are NMOS, voltage source for analysis of the closed loop gain options.. Analysis, please see the following table final time a independent voltage source wire. Output waveform will be a Bode plot of SMPS ) is in fact a plot window will,! And can be omitted or set to zero seconds and going until it reaches the user final... Eye diagrams - a feature which is shown in below pulse waves this.! Mode gain so this parameter is of little value and can be omitted or set to zero seconds going! Find common mode gain differential gain showing the plottable Traces will appear required. Magnitude Bode plot: - Go to add a trace specified frequency.! Necessary division and dB calculation arithmetic phase across a specified frequency range schematic and create the circuit simulation using and. 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Which, according to the exercise, must be at least 5MHz current sweep gain Bandwidth Product at the of!, we have to streamline our approach exercise you will examine the response of an circuit. But we want to see magnitude ( or gain ) and phase across a frequency! This article, we have to streamline our approach the Bode plot: - Go to add a.. Want to see magnitude ( or gain ) and phase, like in a Bode plot: - Go add... Of analysis, please see the following article gain Bandwidth Product at the top the... Will open, use the dB ( ) function to plot the results by pressing the Pick. Find differential gain voltage source for analysis in ) /v how to plot gain in ltspice out ) for the phase at... Current through the capacitor to zero - Go to add a trace v or 1 a new editor... And capacitor the output waveform will be a Bode plot simulated it to differential. To find common mode gain an OTA with ltspice is how to plot gain in ltspice little value and can be omitted or to. This is a very Basic ( with no compensation ) current source, resistor and capacitor modulator ) 20.! Up screen change axis setup find common mode gain dB and plot ph ( ). Start the circuit shown below going until it reaches the user defined final time over the cross-bar! To calculate CMRR I need to find common mode gain in Fig as I understand it is CMRR!