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Re: Bandgap Reference Vdc analysis problem! bad results- HEL
A piece of advise to you is to plot the DC analysis graph for temperature.
From your bandgap structure, you should get a Vref of about 1.2V usually, but it can depend on your process. By increasing the value of R2, your Vref...
There is no spec really. The threshold value can be between 100mV ~ 240mV. It needs to operate from -40 ~ 85 degree. It's supposed to be used as an enable detection device. When the enable signal is above 150mV, the IC turns on. As a result, no other circuits are available because the IC is...
Thanks for the reply.
If I were to use a comparator you mentioned, I would need a bandgap reference to generate the 0.15v. A normal comparator + a bandgap reference that operate under 0.3uA total quiescent current doesnt seem reasonable.
I was thinking more of an easier approach that probably...
I need to design a cheap comparator that requires almost 0 quiescent current (0.3uA to be exact). Basically the output goes high when the input > 0.15v, otherwise it's a low.
Can somebody provide some ideas/suggestions?
Many thanks,
how to calculate impedance
you didnt specify where the source of the transistor is. I am assuming the input port is connected to M1 and M3's source. In that case, your input impedance should be very small ( ~ 1/gm)
Re: high voltage MOSFETS
Could you please tell me why the drain extention under gate makes this a high voltage device?
Also, I also noticed some devices used wells instead of LDD for the drain extention. Is there any advantage/disadvantage for this?
thanks
startup circuit
1. I think it is right, but you have to make sure your initial conditions are reasonable.
2. In the zero state, bandgap reference output would be very low. It will be stuck there forever and never start.
about thermal shuntdown
one way to design thermal shutdown is to utilize BJT's dependancy on temperature. You can find the VBE of the BJT at the shutdown temperature you want and compare it with a reference voltage you generated from your bandgap.
poly resistor negative temperature coefficient
You would need a voltage that is CTAT. If your voltage and resistance both decrease with temperature at the same rate, you would get a temperature independent current.
To generate a CTAT voltage, VBE of a BJT would be a good start.
1. It depends on the structure of your bandgap. With your structure, it is the case.
For the opamp to be stable, we want to ensure overall negative feedback. The negative feedback factor has to be greater than the positive feedback factor. We want the side with the resistor to be connected to...
your op-amp has little to no effects on the TC of your bandgap reference.
Also, 35ppm/k is good enough already as far as I know. Unless you are talking about the curvature correction design, which might take 35ppm/k as poor performance.
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