[sdiy] An Improved Sine Shaper Circuit

René Schmitz synth at schmitzbits.de
Wed Apr 22 23:40:03 CEST 2020

Hi David, Don and all,

So, let me try this newfangled image posting thing too....

On 22.04.2020 07:55, René Schmitz wrote:
> On 21.04.2020 22:24, David G Dixon wrote:
>> In what way does the output of the diff pair not look like a sine wave?
> If you would subtract the two, you would see it a bit better.
I just now realized you were referring to the statement of Don, 
regarding the diffamp output not being remotely close to sinusodial.
The Thomas Henry circuit you posted, is another thing entirely, so this 
does not apply here.

Find attached a simulation of the ar317 sine shaper. The collector 
currents are more triangle than sinus. Just a lightly bent triangle.

What one can also see is that the circuit is certainly not optimal. (But 
they could be from my simulation.) More like 40dB down.

What we can also see is that the current that goes through the resistor 
that feeds in the triangle (R18), is of the same order of magnitude than 
the "bent" triangle that comes from the transistor.
The sum of these two forms the sine.

If anyone wants the ltspice file, let me know.


synth at schmitzbits.de
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