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