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For a conventional bandgap, if sweep temperature from -40 to 120, the bandgap output voltage is like this. In the figure, the max V is 1.206V at 35℃, the min V is 1.199V at 120℃. My question is how to decrease this variation?
Vout=Vbe+△Vbe*R2/R1=Vbe+kT/q*ln(n)*R2/R1
Which factor will affect...
Re: How ot take screencapture of waveform output from simula
Analog Design Environment->session->options->waveform tool: AWD
By the way, I prefer AWD than wavescan, for wavescan is alwayse slower than AWD.
Let's evaluate the current mismatch due to vt mismatch.
For saturation,
I=k(Vgs-Vt)^2
so
△I/I=△Vt/(Vgs-Vt) (1)
For sub-threshold region
I=Io*exp( (Vgs-Vt)/m(kt/q) )
△I/I==△Vt/m(kt/q) (2)
compare (1) and (2), Vgs-Vt >> m(kt/q)
so current mismach in subthreshold region is much larger...
degeneration emitter resistors in current mirror
Increases the output resistance will reduce the effect of mismatch between transistor parameter. They are same case.
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