Subject: Re: Determining bjt noise parameters for Spice models?
Date: Fri, 13 Dec 2002 08:38:03 +0100
Organization: Wanadoo, l'internet avec France Telecom
References: <3DF6537E.B0FC9DBE@worldonline.fr> <3DF90203.C9691374@worldonline.fr>
NNTP-Posting-Date: 13 Dec 2002 07:38:04 GMT
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Kevin Aylward wrote:
> A.Iakovlev wrote:
> > Kevin, Thank you.
> > Kevin Aylward wrote:
> >> Just about. You need to make sure the base resistance is set right.
> >> This is the main variable that distinguishes transistor noise form
> >> exh other. Other noise contributions are inherently fixed by Ic and
> >> hfe. So, after the 1/f curve flattens out, set rbb until the flat
> >> portion reads correctly. Do this at a highish collector current, e.g
> >> 10ma, also with r source set to zero.
> > I've tried to do this at 10kHz in the following way:
> KF needs to be set at a low frequency, say 10 Hz.
I've started with the thermal noise, estimating that the flicker noise
vanishes at 10kHz. Was it a wrong approach?
> > - common emitter;
> > - collector connected to a voltage source in series with a resistance;
> > - base directly connected to a voltage source (VSRC, small AC);
> > - the base voltage source adjusted to get about 10mA collector
> > current;
> > - equivalent input noise calculated as V(ONOISE) on the collector
> > divided by the gain calculated (by Spice)
> > on the input AC.
> > Doing that with the standard 2SC3329 model and varying RB from 2 to
> > 10 Ohm could not reach the 0.6nV/rtHz specified by the datasheet -
> > much lower levels obtained; the datasheet announces rb about 2Ohm.
> I dont understand whatvyou say here. Is the spice value too high or too
Sorry. The value calculated (not directly by Spice but by me, from the
V(ONOISE) provided by Spice) was much lower than 0.6 nV/rtHz.
> Kevin Aylward
> SuperSpice, a very affordable Mixed-Mode
> Windows Simulator with Schematic Capture,
> Waveform Display, FFT's and Filter Design.