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20 Threads found on edaboard.com: Resistor And Variations
I am designing a 10uA contant current as reference current. I have designed a bandgap reference voltage of 1.2V. In order to generate 10uA constant current, I use a feedback OP drive PMOS to pass 1.2V voltage to 120k resistor. The resistor 120k is too large to be implemented in CMOS process. Can I have other solutions? Thank you.
I have a CMOS LCVCO with tail resistor only on top to provide bias current. Between this resistor and sources of cross coupled PMOS transistors, a big decap is added (~70pF). The VCO can start oscillating at TT corner, but couldn't at SS corner. If the big decap is removed, SS corner can work. What could be the reason? Thanks in advance!!
OK, I get the common emitter, common collector and common base configurations according to the transistoramp amplifier design software I downloaded. But there seems to be a bewildering array of variations on this theme. Some where collector resistor is not used, some where the emitter resistor is not used, some where only (...)
It isn't a very good circuit for voltage detection. While you have calculated for one value of hfe, what about other extremes? and Vbe variation? and temperature variations? A couple of possible improvements would be to add a resistor from the base to ground. You should make the base current a lot lower than the current (...)
Dears, I need to build Solar Tracking system. I am interfacing FPGA-Cyclone2 with ADC0820(datasheet attached). The ADC is intended to get voltage variations from the resistance in series with Cds photo resistor and forward the values to FPGA. LDR Circuit is attached. I am a totally newbie to FPGA and ADCs (...)
How exact is exact? Without adjustment, you should expect a few percent duty cycle deviations due to imperfect 555 threshold voltages. The period will be also affected by threshold voltage variations and capacitor and resistor tolerances. The datasheet says about 2 % initial accuracy for astable period. 5 or 10 % would (...)
hello guys... As the title states, what is the smallest value of resistor that can be reasonably put on chip. I will be using the 0.25micron standard process. I need it to be small so that efficiency will not suffer. Thank you.
Hi Charles, A very common way is to use a operational amplifier to force the voltage across some resistor equal to the bandgap voltage (~1.2), therefore, generating a current almost independent of the temperature. However, due to the resistor process variations, this current can vary more or less 20%. I don’t think (...)
The bandgap voltage spread is defined by the offset voltage spread of the control amplifier and the current mismatch of T4/T5. The used bipolars could have an impact depending on the amount of voltage drop of the internal emitter resistance. That resistor re*(1-1/12) have to be compared to the 200 ohm resistor (...)
The main factors affecting switching time is the 'Total Gate Charge' which is usually given on the data sheet in Nana Coulomb's, and the 'Turn-on/Turn-off delay times. But there are variations in these parameters from device to device. Below is an extract from a switching loss calculation. Calculating the mosfet switching loss is diffi
Hello, how can I design a Gohms resistor which remains fairly constant with variations of the voltage across it? Thanks
If you are achieving BW improvement just by changing the loop parameters, it normally takes a higher valued resistor and much lower valued major cap for the same phase margin. This means higher spurs at the vctrl node. PFD-CP mismatch induced spurs can show variations with reference clock period but not with BW. The spur is observed in (...)
For best match, current flow should be in the same direction. This may seem like overkill however there are a few reasons why this is the case. The largest contribution to resistor mis match is not L or W variations especially in close proximity. Even the lack of dummy resistors either side of an array can have secondary effects to (...)
No. If you want less than 2mV overall accuracy over temperature and corners then the olny way to compensate for process variations is trimming. You can trim the resistor which is in series with BJT/diode.
Your question my friend is extremely abstract. You can use your transistor as a sensor of : 1. Current 2. Voltage 3. Temperature (for big variations and under special circuitry). More efficiently you can use the transistor as a capacitor or a resistor. Of course there is the vast category of MEMS ( Micro Electrical Mechanical (...)
mos resistors suffer from process and voltage variations.
30 years ago it was standard practice to put dummy resistors at the outside of resistor networks. These were there to produce the doping gas turbulence before it reached the real resistors.
1. Normal distribution is a good approximation for most random deviations. Note that the variation in a certain parameter (for example the resistance of a resistor) results from the variations in a significant number of physical quantities (in our example, thickness of the conducting polysilicon layer and the concentration (...)
This is self biased current mirror configuration . R=1.8-(3Vov+3Vt)/I ; Vov=overdrive =50mV R approx is 60 ohms ,calculate W/l for pmos and nmos . The bias current has resistor variations that needs to be accomodated in design .
Shot noise is current variations. In a SPICE type simulator you could use a resistor to generate noise and then an ideal voltage controlled current source. These type sources are a device type in the SPICE devices.