Hello sir As derivative of. CTAT voltage is varying across temperature, so for scaling PTAT what value of CTAT derivative we should take for calculation such that the scaling is valid for all temperature range. Can u please guide Thanks

@ First of all, the principle is that you add a CTAT voltage from the vbe of the bjt to a scaled PTAT voltage. The temperature coefficient of the CTAT voltage is about -2mV/degree C. When you simulate it, you can see value in your process. The PTAT current is made using a PTAT voltage drop over a resistor. This resistor is normally a high resistivity polysilicon resistor. When you make the Bandgap voltage you source the ptat current through poly silicon resistor in series with a diode connected bjt, to ground. The voltage drop over the bjt will be roughly 650mV. You have to scale the size of the series poly silicon resistor so that the sum gives approximately 1.25 volt at room temperature. The means a voltage drop over the resistor of (1.25 - 0.65 = 0.60 volt). Make a DC analysis in SPICE and you will see the bandgap voltage as a parabolic voltage, it should be with its max voltage at room temperature. For matching use unit resistors that you place in the same direction. Use more than minimum width of the resistors. Use the same unit size and width as in the PTAT generator. Happy New Year.

Thank you sir for your guidance, I will try this.. Happy new year to you!

me also

I will help you with what I know. We are using BJT in the first place because we want to imitate diode characteristics. In a diode, we will have exponential relationship between voltage and current( Id = Is*exp(Vd/Vt) ). This is seen in a BJT as well ( Ic = Is* exp(Vbe/Vt)). But a MOSFET has a linear relationship with voltage in linear region and a quadratic relationship with voltage in saturation region. So we do not use MOSFETs in place of BJTs.