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