# Questions tagged [thd]

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### How to reduce THD in a Cs amplifier while maintaining Vout?

As part of my assignment, I need to design a Cs amplifier with certain fixed values. The output voltage peak-to-peak (Vout,pp) must be greater than 2.5V, and the Total Harmonic Distortion (THD) must ...
• 11
35 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 ...
85 views

### How do I calculate the THD of a given spectrum analyzer waveform?

The spectrum analyzer reference level is 0 dBm. The fundamental level is 3.16 dBm. The second harmonic value is -9.51 dBm. The third is -10 dBm. 4th is -19.89 dBm. 5th is -25.32 dBm. 6th is -23.46 dBm....
133 views

### Why does the current THD increase and voltage THD decrease when increasing the inverter switching frequency?

I have a three phase inverter model and I am investigating the effects of an increased switching frequency for pre-defined LC filter parameters. It is a simple MATLAB Simulink model: DC source, ...
• 59
389 views

### How to extract ENOB from LTSpice simulation and see the effects of oversampling?

I have a fully differential instrumentation amplifier circuit with a gain of 536 to map a 3mVpp signal (centred around 1.65V) to +/-1.6V, as shown here. My signal bandwidth is 250Hz, and I would like ...
• 155
131 views

### What causes the large THD increase measured after the output resistor in this op-amp stage?

I'm designing an audio mixer and took good care to create a relatively low THD signal path. At the final output stage I'm measuring a a THD of 0.06%, (10 Vpp, sine @ 1 kHz.) This is measured directly ...
• 1
1 vote
177 views

### Designing bandpass filter for audio amplifier

I am a 3rd year engineering student currently working on a project where I need to basically make an ultrasensitive metal detector. Basically, I need to create an alternating magnetic field by ...
300 views

### Generating and measuring a sine wave with THD below -80dB

For an experiment I need to generate a sine wave which has a THD below -80dB. I would like to do that using a band-pass filter connected to a function generator because the output of the function ...
• 343
144 views

### Waveform distortion with high ohm resistor [closed]

I have a problem that waveform distorted after adding high ohm resistor, (second figure shows that resistor voltage which doesn't follow of input pulse (yellow). So I added Darlington pair right after ...
393 views

### Reason for frequency steps shown in Simulink FFT analysis tool

While using the FFT in Simulink tool, I have observed that if more number of cycles are selected then frequency steps in which harmonics percentage is shown is also divided accordingly. For example: ...
1 vote
1k views

### How to reduce THD of amplifier circuit

I am pretty new to designing amplifiers, but I have been playing with LTSpice and came up with a schematic, however I am not sure how to reduce the THD of the circuit. For 1kHz, I get the following ...
183 views

### How to calculate THD using only the first harmonic?

How can I calculate THD using only the first harmonic? How can I implement in C code DFT voltage formula in order to calculate THD?
1 vote
471 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 ...
• 31
2k views

### DAC "aliasing" of harmonics

While reading articles and application notes regarding DACs and their output spectrum, I stumbled across aliasing of higher harmonics to the first Nyquist band. For example, when generating a single ...
• 75
61 views

### Relation between THD and spectral leakage or number of samples

So I'm studying data acquisition and on the lab had to perform an experiment involving sampling a sinusoidal signal of frequency 1100 Hz, 70 samples and sampling frequency 22000 Hz. Now I can clearly ...
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