This is a continuation of this post.
Below is a table describing the results of Fourier Analysis up to the 15th harmonic and the Total Harmonic Distortion (THD) at 1kHz frequency for circuits with no NFB or with NFB and different types of OpAmps as the differential input stage. With no Negative Feedback applied, the crossover distortion rises the THD to about 20%. Applying a simple feedback network with an opamp as a differential input stage the THD drops below 0.1% and with NE5534 precision opamp it goes further down to 0.00019% a very acceptable level. We see, that we can decrease THD at very low level, even without a sophisticated bias network or other linearizing sub-circuits.
With LM741H or TL072, the THD has dropped and the odd harmonics play a dominant role in the harmonic content. On the other hand, NE5534 decreases the whole harmonic content very much, with even harmonics having a greater share this time.
Below is a table describing the results of Fourier Analysis up to the 15th harmonic and the Total Harmonic Distortion (THD) at 1kHz frequency for circuits with no NFB or with NFB and different types of OpAmps as the differential input stage. With no Negative Feedback applied, the crossover distortion rises the THD to about 20%. Applying a simple feedback network with an opamp as a differential input stage the THD drops below 0.1% and with NE5534 precision opamp it goes further down to 0.00019% a very acceptable level. We see, that we can decrease THD at very low level, even without a sophisticated bias network or other linearizing sub-circuits.
With LM741H or TL072, the THD has dropped and the odd harmonics play a dominant role in the harmonic content. On the other hand, NE5534 decreases the whole harmonic content very much, with even harmonics having a greater share this time.
| Description | Fourier Analysis | THD @1kHz |
| No NFB |  |
20.019% |
| NFB with LM741H General Purpose OpAmp |  |
0.0789107% |
| NFB with TL072CP JFET-Input OpAmp |  |
0.0231932% |
| NFB with NE5532 Low Noise Audio OpAmp |  |
0.00794657% |
| NFB with NE5534 Low Noise Audio OpAmp |  |
0.000198106% |
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