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    Voltage Controlled Oscillators & FM demodulator

    If the VCO tuning response is not linear, the center frequency will not be deviated by equal amounts by the modulating signal, if it is a pure sine wave for example. When this signal gets demodulated  this will show up as distortion in the recovered sine wave. FM detectors with some of the best...
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    Trying to find transistor

    http://www.st.com/stonline/products/literature/ds/7559.pdf
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    Ft of the transistor

    Here's plots from swcad using vendor coils from their library with Q of about 100, which is about normal from winding a 100nH coil. Feedback cap is set at 10pF. Now the collector current does not go under zero. Vc is the voltage on the collector, Ic the collector current and VL the voltage over...
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    Ft of the transistor

    So, how do we get more power? Well running the osc on 9V gives us almost 8mW drive and higher harmonics, which gives us about 130mW on the power curve. The problem is that now the frequency will drift as the 9v battery gets flat. So no easy answer apart from adding another amplifier stage.
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    Ft of the transistor

    Finally, I biased the amplifier stage into class-C with removing the 47k resistor and adding a RF choke to gnd on the base. I ran a power sweep again. Now we can see that if we can get the drive level up to about 8mW (which it seems we can't) from the simulation data, it is possible to get up to...
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    Ft of the transistor

    Next I increased the feedback cap to 22pF. Now the drive level was near 2.6mW (17 times higher), BUT note the rapid rise of harmonics from the osc (green circles) and we are no longer on the linear part of the power curve. The amplifier is now heavily into gain compression. Output of F1 is now...
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    Ft of the transistor

    I did some more simulation to show the effect of increasing the feedback cap on output level and harmonics. First I took just the output stage and performed a RF power sweep on this stage to determine the maximum output power and gain compression. Then I measured the drive level in mW into the...
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    Ft of the transistor

    AC load line and fundamental power with 100k base reistor
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    Ft of the transistor

    http://www.electronics-lab.com/forum/index.php?action=dlattach;topic=10866.0;attach=9361;image Hi AG, Are you sure about this? Using a non-linear simulator with vendor non-linear models for the transistor and coils (Q value 200), shows that the collector current never gets to zero, and the...
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    Redesign Elektor gigant2000 Amplifier

    Maybe you should send an email to "Self" regarding your views, he welcomes any commentary!
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    Redesign Elektor gigant2000 Amplifier

    It is anybody's right to disagree  :) Just remember that these statements are made by persons that are considered world renowned authorities on the subject and have presented numerous studies and papers to bodies like the IEEE and other professional publications. They have backed up their...
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    Redesign Elektor gigant2000 Amplifier

    From another author: Randy Slone's book Enthusiasm for class A today is often supported by a variety of misunderstandings and myths. The following list provides some major examples. 1. "Crossover distortion in class B is a constant. At low listening levels, it becomes very prominent." This...
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    Redesign Elektor gigant2000 Amplifier

    The quotation and paper refers to audio power amplifiers and not small signal op-amps.
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    Redesign Elektor gigant2000 Amplifier

    Here is a good explanation about the subtle differences between biased Class-B and AB From the works of "Wang & Chien" It is important to realize this. Many people and even most engineering text books get this part wrong or don't understand the difference.
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    help transconductance amplifier

    I made the 1k resistor on the inverting input R3 because you have multiple R2's From writing the nodal equations for the opamp and solving: Without the capacitor across the feedback resistor G(s) = (R2 + R3)/R3 = 48 With the capacitor  added G(s) = (R2 + R3 + R3.C1.R2.s)/(R3 + R3.C1.R2.s)...
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    Redesign Elektor gigant2000 Amplifier

    Another problem with feedback is that you need to increase the slew rate BW of the front end gain stages including the feedback network by the factor of feedback (40 to 50 times) to prevent/minimize dynamic intermod distortion. This was the reason so many transistor amplifiers sounded so bad in...
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    Redesign Elektor gigant2000 Amplifier

    In a recent published Master
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    help transconductance amplifier

    You think? What do you understand under transconductance?
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    Redesign Elektor gigant2000 Amplifier

    The jury is still out on TIM. Some people believe this distortion to be caused by a combination of other well known distortion types. One of the misconceptions is the square wave output testing into a capacitive load, measuring the overshoot-ringing to evaluate transient response/distortion of...
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    Redesign Elektor gigant2000 Amplifier

    The detectable distortion with low order harmonics present is about 1% Crossover distortion can be detected at levels under 0.3%
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