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how to design Bandgap reference circuit

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ethan

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design of a bandgap reference in 0.35um

Hi there,

Anybody can refer me to some resouces about how to desig Bandgap reference circuit step by step?

I need to design a self-biased bandgap circuit in 0.35um technology, which looks like the pic below? Can anyone tell me how to start it?

Appreciate your help.

ethan
 

step by step bandgap design procedure

Do you think whether I can add two pnp BJTs under the bottom of the following self-biasing circuit with some calculations?
 

bandgap reference circuit, pspice

Way to design it would be to 1st simulate the BJT I-V curves and then find the biasing current you need in them , then size the MOS transistors to support that current in saturation. (Writing the equations first and deriving everything will be quite helpful). Also simulate and calculate the negative temperature coefficient for Q3. Then find the current expression in the resistor above Q3 and its temp coefficient expression. Now just set the sizing parameters so that they absolute values are equal. Then just simulate and you may just need to tweak some parameter to increase or decrease the temperature coefficient of the current in the resistor, and thus get a constant Vref.
 
bandgap reference step -patent

Normally, the SPICE model is not very accurate. So, trimming is necessary for the first run.
 

Firstly,i think the first figure can not implement the bandgap with power supply smaller than 4v. Because the left bias is cascoded with four diode between two power supply, it causes the circuit works well in small margin range of power supply.

1. the design steps are determing the two legs current bias with respect to the power dissipation;

2. make sure the pnp unit emitter area current density, so to sure the ratio with two legs of pnp and consider the layout matching; Then, the resistor is determined by the ptat current;

3. in corresponding with zero TCF, make sure the pnp and resistor value;

4. maybe , i think a op amp shoud be used for stability the same level;

5. the last is to design the start-up circuit;
 

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    ethan

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Hi! Can you tell me how to get the widths and lengths of your transistors in the first part? thank you
 

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