why the curve of bandgap is not concave,but protruding

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incol

Joined: 18 Jan 2005
Posts: 97

01 Apr 2005 12:38 why the curve of bandgap is not concave,but protruding

why concave is wrong

mike_bihan

Joined: 21 Mar 2002
Posts: 259

01 Apr 2005 13:51 why the curve of bandgap is not concave,but protruding

2nd order tempco derivitive should be negative.

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Vamsi Mocherla

Joined: 06 Sep 2004
Posts: 482
Helped: 62

01 Apr 2005 14:52 Re: why the curve of bandgap is not concave,but protruding

Well, the bandgap tempco voltage consists of two parts, Voltage due to the PTAT current over a resistor and -ve coefficient voltage, VBE. The PTAT Current is due to the ΔVBE/R of the input loop. Hence the final voltage will be responding positively at lower temperatures and to the VBE at higher temperatures. Hence you get a convex shape.