[sdiy] MOSFET ANGST

[Scott Gravenhorst]

Peter et al,

Yes, I made much of it go away using the linearizing resistor technique, but I
got unsatisfactory results with respect to amplitude.  I couldn't get much
more than 100 mV of input signal before I started seeing soft clipping of the
triangle peaks.

So unless I get some brainstorm that presents an idea for allowing a much
larger input signal (I need about 3 volts for my application, preferrably
more), this method will be shelved.

Today I will experiment with an H11F1 and see how it performs.  I'm not
encouraged, however, by the datasheet, I actually don't expect much more than
the MOSFET VCR.

I shall post later today about this simple voltage controlled attenuator
experiment.

Peter Blackett <dragon.servicing at virgin.net> wrote:
>Dear Scott Gravenhorst,
>there was a discussion about using the 2n3819 as a "soft switch " for
>Organ stops at one of the Electronic Organ construction Society meeting
>I went to .one of the probelms mentioned was that you did get
>assimetrical distorsion while the swicth was opening and closing .
>regards Peter 
>
> wrote:
>> 
>> I have started doing a few experiments, simple stuff just to see if what is
>> supposed to happen actually does.  So I built a little voltage controlled
>> attenuator.  It sort of works...  read on.
>> 
>> Please see http://home1.gte.net/res0658s/MOSFET_test.gif
>> 
>> In all cases, the AC input is a triangle waveform from a signal generator.
>> 
>> I started with "A" and noted what I would call unkindly behavior.  At zero
>> gate volts, the output is "full scale" and looks like a proper triangle
>> waveform.  However, as I increased the gate voltage, generally, the
>> amplitude of the output was attenuated as expected, but there is
>> assymetrical distortion.  I looks like as the gate voltage increases, the
>> negative portion starts to soft clip _first_, then after the voltage
>> increases more, the positive portion begins to drop in amplitude, but no
>> soft clipping occurs!
>

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