# Higher order effects of CTAT and PTAT when testing a BANDGAP

I want to use candence to simulate the real behavior of a voltage reference and so far I found circuits that are based on the ideal models.

What non linearities can I introduce in this ideal model of testing a part of the bandgap circuit? On the pins vD and v2I have to connect an opamp.

Proposed solutions are resistors or transistors in stead of the ideal current mirror. Is this a good approach?

Thanks!

• Why do you want to introduce non-linearities? The Vbe of the transistors has a non-linear current-voltage relation. The opamp + two resistors is simply a way to implement both current sources. Is this a good approach? That depends on your goal. What is your goal? – Bimpelrekkie Nov 5 '19 at 13:53
• @Bimpelrekkie to get the feeling of analog design and what I should expect when I am using all of the possible non linearities. Is it not better (also used in real cases) if I use mos transistors instead of the ideal case? – electricalEN Nov 5 '19 at 14:00
• You keep talking about "non linearities" but what you actually mean are "higher order effects", for example: the $i_o$ current sources are ideal and have an infinite output impedance. If you would replace the current sources with resistors and an opamp the output impedance would no longer be infinite. "Is it not better..." no, using real components will make performance worse. But what you mean is: performance will get closer to reality. You cannot buy an ideal current source so you better take into account the effect of a non-ideal source has. – Bimpelrekkie Nov 5 '19 at 14:16