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It is clear from your sim results that something is wrong. Your DC gain is negative, which is indicitive of something is not biased right or something. You should be seeing a gain of at least 40-50db with that amp. You shouldn't be seeing -50dB. Something is wrong with your setup.
Most oscilliscopes have a single sequence trigger function that you should be able to use to see your spike. I don't know if your particular scope has it or not, but even the most basic newer scopes have this function today. It is critical for finding things like voltage spikes that are not...
Re: too much voltage drop
You use the resistor divider to set the output voltage but not the way you are doing it. Basically take what you have and connect the node where the 2 resistors meet to the middle pin. The reference voltage is supposed is supposed to be 1.25V. Based on that you can...
folded cascode biasing
It doesn't matter if you keep Q3 and Q4 in saturation because you aren't getting any gain from those devices. however depending on how you bias VB1 you are basically clamping that drain of Q3 and Q4 to VT+excess voltage above VB1. So they will stay in saturation if you...
I am not really sure where you are getting stuck, but ohm law is V=IR so I=V/R
If you know V and know R you can always calculate I. It doesn't matter how the resistor network is set up if, whether the resistors are in series or parallel or whatever, if you know the voltage across a resistor...
Re: LED current regulation
The emitter degeneration resistors are critical. Adding emitter degeneration makes the matching of the NPN's mirrors much better(NPN current mirrors is basically what you have).If you do the math you'll see that emitter degeneration inmproves the current matching by...
Re: LED current regulation
The concept is OK. Your matching is going to depend on the NPN matching as well as the matching of of the emiiter degeneration resistors. So depending on how tight you need the current matching to be, you may or may not meet spec.
Also, you have to be careful...
Re: Ron in triode.
I have never heard of anyone being able to make RON independant of process and temperature. If someone was able to do, they would have process that is so good, they would dominate the market in the power managemen field because they would be able to keep their efficiency...
Re: Circuit desing
There is no one size fits all for sizing MOSFETS. That is why you generally just FETs shown without the size. The sizing is going to depend on what your circuit needs to do and the process on which you are designing.
Sizing is going to depend on several things like...
Once VREF falls below a diode drop, Q3 shuts off and is high impedance. Basically, the VREF node will be clamped at a diode drop with respect to Q3/ With the VREF node being high impedance you have no way to discharge that node, excpet for leakage current. It will eventually discharge if you...
bode plot: half power point
"Yes, but remember: only for first order circuits ! "
Thats true but it is a pretty good estimate unless you are really pushing the bandwidth way out.
3db in frequency response
Because the 3db point is a convienent point to use. It represents the point at which the output power has dropped to 50%. It is also useful because the 3db point represents a 45 degree phase shift which is a nice number to understand what is going in regards to the...
two-stage comparator design
An unstable opamp is a comparator. You don't need any compensation if you want to use your op amp as a comparator. You want the comparator to peg rail to rail, very quickly, with a very small delta at the input.
If you left the compensation in, the circuit would...
Re: Bandgap Problem!!
Most of the questions were already answered in the first post but I'll add a few comments.
1. 8 to 1 is typically used so you can layout the device with the 1X device in the center and the 8 devices built around the 1X device. That is why you typically see 8 to 1. You...
Re: GND issue
In regards to the ESD ground.
Lets say you only have two grounds DGND(digital ground) and AGND(analog ground). Your ESD devices are going to be tied to one of the ground lets say DGND for this example. Now if the Grounds have seperate bond pads and are bonded to different pins...
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