# Questions tagged [total-harmonic-distortion]

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### What exactly is the influence of the carrier wave signal in the case of a PWM-controlled 3-phase inverter?

How exactly does the value of the PWM-frequency of a 3-phase inverter contribute to the output voltage and current waveforms of the inverter? How can the choice of this frequency influence the output ...
• 133
1 vote
53 views

### Can a PFC converter work if input AC voltage is distorted (having harmonics)?

I see the assumption that the input AC volatge is clean (pure AC), in almost all PFC explanation articles. What if the input AC has some harmonics, say a volatge distortion factor of 10%, would it ...
• 3,072
143 views

### Issue with formula for Total Harmonic Distortion of a pure rectangular switching function

The known value of THD for a pure rectangular switching function, for which the duty ratio D = 0.5, is 0.483 or 48.3%. I have tried to back-calculate this using formulae for THD in order to work out ...
1 vote
150 views

### Efficient method of measuring total harmonic distortion

I have been trying to create a set-up for measuring (estimating) the reported total harmonic distortion of an op-amp. (Please don't ask why I don't use a spectrum analyzer because I have been assigned ...
• 338
36 views

### How is the THD of a signal calculated? What is the process inside of an automatic distortion meter?

In general, the equation to find the Total Harmonic Distortion (THD) is: $THD = \frac{\sqrt{V_{2,rms}^2+V_{3,rms}^2+V_{4,rms}^2+V_{5,rms}^2+...}}{V_{1,rms}}$ According to attached figure (A Course ...
160 views

### Abnormal THD values for Audio Amp in any circumstances

Using Charles Wenzel's "High Gain and Fidelity Audio Amplifier" (source:https://www.radiolocman.com/shem/schematics.html?di=335167) as my final project for my freshman year due this Saturday,...
66 views

### Why does my THD-value not converge in simulation of rectifier circuit?

I'm trying to simulate a FWR - circuit with an RC-load. In doing so, I want to analyze the THD-value of the circuit. In the end, I've tried changing the FFT-points, increasing and decreasing the ...
• 313
93 views

### Is harmonic distortion only a problem for the power company?

I know that harmonic distortion is a problem for the power company because it influences the power factor, but what about me as an end user? In my situation I would use 9 drivers of 200W (230VAC/48VDC)...
• 119
218 views

I'm trying to solve the VAS (voltage amplifier stage) loading distortion in a three-stage amplifier. Excluding the input stage (called IPS in the circuit below), here is represented a typical VAS ...
• 33
239 views

### Why am I measuring such high THD+N on my active high-pass filter?

I have designed a 2nd-order active Sallen-Key high-pass filter for use in an audio circuit. An LTspice schematic is shown below, where VDD is 5 V. I have also breadboarded the circuit using low ...
• 115
66 views

### S/N ratio or distortion analyzer

I'm having trouble finding an affordable low bandwidth analyzer solution for measuring audio spectrum performance (20KHz and below). Does anyone have a suggestion for buying (new / used) or building ...
• 13
260 views

### THD calculated with amplitude instead of RMS

I have a digitized sinewave, and want to determine the THD of this waveform. This is the equation I am familiar with for calculating THD:  THD=\frac{\sqrt{\sum_{n=2}^{\infty}V_{n_{rms}}^2}}{V_{fund_{...
• 143
369 views

### Difference between THD equation and design circuit current

Why does the summation of design circuit current equation (Ib) start with 1 while for calculating THD the summation starts with 2?
72 views

### Total Harmonic Distortion fundamental frequency clarification

I have a voltage controlled amplifier that I would like to calculate the THD of using the power dissipated at the (resistive) load. My question is: if the input voltage frequency is 100Hz, would I use ...
• 539
1 vote
484 views

### Accuracy when measuring THD with LT Spice for AB Audio Amp

I've designed and built my own AB class audio amplifier circuit. I designed it to have as low THD as possible, using LT Spice to run my simulations with the .four command, so I created a bunch of ...
• 41
2k views

### Calculate total harmonic distortion

I have the following problem. MY ATTEMPT I found the formula for the total harmonic distortion to be this: $THD = \frac{\sqrt{V_2^2+V_3^2+V_4^2+V_5^2+...}}{V_1}$, where the subscript denotes the ...
• 4,261
814 views

### THD analysis of an arbitrary expression in LTspice

Is it possible to perform .four THD analysis of an arbitrary expression in LTspice? It works seamlessly with simple expressions like ...
• 123
2k views

### How to calculate total harmonic distortion in PSpice?

How can I calculate the total harmonic distortion of a sinusoidal Oscillator in Pspice? I am using eldo and ezwave for the simulations and waveforms.
1 vote
327 views

### Total harmonic distortion and DFT

I am trying to understand a design that would enable us to measure/determine the total harmonic distortion. Key points: The system is microcontroller (TI, C2000, dual-CPU) driven electronic It has a ...
• 1,670