SPICE-Simulation using LTspice IV

More documents

Recommendations

Info

Example: Let us use the RC-LPF of the last chapter (R =10k / C = 10nF). The input is fed by a symmetric square wave voltage (minimum amplitude value = 0V , maximum amplitude value = 1V , frequency = 1kHz). If we use a simulation time of 20ms with a maximum time step of 100ns we meet the above recommendations as follows: a) The simulation time of 20ms is an integer multiple of the signal’s period time (1ms). b) A maximum time step of 100ns is corresponding to a minimum sample frequency of 1/100ns = 10MHz. This gives a Shannon corner frequency of 0.5 x sample frequency = 5MHz. c) The number of true samples is 20ms / 100ns = 200 000. So we enter in the FFT menu. „131 072 sampled data points in time“ Now draw the circuit, set the properties of the voltage source, choose simulation time and time step and write the directive to switch off the data compression. The time domain simulation result (= input and the output voltage) should be presented in two plot panes. Also “thick lines” are used for the curves (= button with the hammer / menu “waveforms”). Now right click on the input voltage and choose “View” and “FFT” 32
Select Input Voltage V(n001) by a mouseclick As discussed we have 200 000 real samples of this curve. So we enter a “number of 131 072 data point samples in time” and start the FFT. This is the successful result: Start frequency = frequency resolution = 50Hz = 1 / 20ms. The stop frequency is 3.3MHz and can only be increased by <strong>using</strong> a higher number of samples. Now change the diagram to linear vertical and horizontal result presentation to confirm theory which says: In a symmetric square wave you can only find the fundamental frequency and its odd harmonics. The amplitudes of the harmonics decrease exactly with their order: Note: If anybody is additionally interested in the phase information: click on the scaling of the right vertical diagram axis and press “Phase” in the menu. 33
Page 1 and 2: SPICE-Simulation using LTspice IV T
Page 3 and 4: 8. Project 4: U-I-Curves of Parts 4
Page 5 and 6: 1. Introduction Modern electronics
Page 7 and 8: 3.2. Presentation of Simulation Res
Page 9 and 10: 3.4. Changing Curve Colours A very
Page 11 and 12: Task: Make the voltage curve visibl
Page 13 and 14: Step 2: Enter the new border values
Page 15 and 16: 3.7. Differential Measurements Ever
Page 17 and 18: 3.9. Changing Part Values Now we wa
Page 19 and 20: 4.2. Changing Part Values This is d
Page 21 and 22: Now start the simulation, click on
Page 23 and 24: 4.3.3. The Impulse Response Fourier
Page 25 and 26: This is the correct presentation: -
Page 27 and 28: 4.4.2. Square Wave (f = 1691 Hz) St
Page 29 and 30: 4.5. Frequency Domain Simulation: A
Page 31: 5. FFT (= Fast Fourier Transformati
Page 35 and 36: 6.2. Important: creating SPICE Mode
Page 37 and 38: 6.2.2. Creation of the Symbol for a
Page 39 and 40: For an ideal transformer you can re
Page 41 and 42: Step 5: self-explainig…. 41
Page 43 and 44: -----------------------------------
Page 45 and 46: When simulating for 200ms, you will
Page 47 and 48: 8. Project 4: V-I-Curves of Parts 8
Page 49 and 50: 8.3. NPN Transistor In the „examp
Page 51 and 52: 8.4. N-Channel Junction FET First w
Page 53 and 54: In the simulation we would like to
Page 55 and 56: 9.2. Two Stage Broadband Amplifier
Page 57 and 58: 9.2.4. DC Bias If you want to know
Page 59 and 60: 9.2.5. Frequency Domain Simulation:
Page 61 and 62: You will see this result and that a
Page 63 and 64: Using the cursor you will find the
Page 65 and 66: Let us now draw the complete circui
Page 67 and 68: 10.3. Use of Labels In general OP A
Page 69 and 70: 11. Project 7: DC-DC Converters Fir
Page 71 and 72: 11.2. The Step Up Converter The sch
Page 73 and 74: If you want: vary the gate voltage,
Page 75 and 76: 11.4. The Step Down Converter In th

SPICE-Simulation using LTspice IV

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?