[sdiy] Discrete buffer distortion

[Jerry Gray-Eskue]

It sounds like you are operating the transistor in the Small Signal region,
in this area of operation the output is non linear, once you hit the large
signal area the buffer should act in a close to linear fashion.

This small signal area is used in the expo converters, sine wave shapers and
several distortion effects to name a few of the applications.

Diodes also have a similar small signal region and can be used in a very
similar manner.

- Jerry

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of cheater cheater
Sent: Saturday, September 26, 2009 6:21 AM
To: synth-diy
Subject: Re: [sdiy] Discrete buffer distortion


Not that I can come up with explanation, but the first quesiton I
would ask is how does it work on real components?

D.

On Sat, Sep 26, 2009 at 5:55 AM, Antti Huovilainen <ajhuovil at cc.hut.fi>
wrote:
> Hi
>
> I've lately been simulating some discrete circuits in spice. One effect
has
> me stumped: when using simple NPN / JFET follower with active high
impedance
> load (to keep Vbe / Vgs constant), the distortion seems heavily influenced
> by frequency and source impedance. The PSU voltage also plays a large
role,
> as the distortion seems to be inversely related to PSU voltage (Vcb / Vdg
in
> particular).
>
> What is the cause of this distortion? I'm guessing it has something to do
> with parasitic capacitance of the transistor, but why does it show up as
> distortion and not high cut? And why is the effect so huge? (1% THD for 20
> kHz 1V RMS signal with J201, +- 4.5V suply and 1 MOhm source impedance).
>
> Antti
>
> "No boom today. Boom tomorrow. There's always a boom tomorrow"
>  -- Lt. Cmdr. Ivanova
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>

_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy