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1000 Threads found on Miller Capacitance
basically, miller effect is the small g-d capacitance multiplied by the voltage gain at the drain. a high impedance at the drain gives a big miller multiplication. however, looking into a source is a very low impedance so the voltage gain, and consequently the miller effect, is smaller.
Do a web search on Google for "What is miller capacitance in MOSFETs" .. miller capacitance is usually given as Cgd capacitance versus Drain to Source Voltage .. see example below .. Regards, IanP
Hi, What is miller capacitance? Why it is used in Differential Amplifier?
what is the effect of miller capacitance on stability? if the miller effect dominates, does it mean that the positive zero is at very high frequency?
Dear all, How to calculate miller capacitance from the model parameters of a transistor that's biased up? Another related question is that when I want to use simple equation to find a particular parameter, say use Cgs as part of ft expression, how to find this capacitance? Since there are Cgs, Csg (for Cgd, there is also Cdg)? Thank you.
Here's an application note which exactly uses feed forward compensation with no miller capacitance, but that's possibly not what you're thinking of. You might want to describe your application.
All transistors have miller capacitance which is from the inverting output to the input. In a differential amp , by adding caps by cross over ( From + out to + in and -out to -in ) from internal differential outputs, it tends to cancel the negative feedback with a lesser positive feedback with non inverting current or negative miller Effect (...)
cascode miller cap.
In Gray it is said single stage opamps,such as the telescopic cascode or folded cascode,have only one gain stage;therefore miller compensation is not possible. Why? Can I attach a miller cap between negative input and single ended output?
If you use Hspice, then it is probably to use LX19(mn) to get information of miller effect.
In simple terms, the miller effect allows a small capacitance to be "amplified", which is useful for compensation. Using a non-miller capacitance for compensation means it will have a larger value, hence larger area.
Hi I want to calculate the output capacitance Co of a transconductor as depicted probleme i dont know how to do to calculate only Co without the contribution of the overlap capacitance here is my
what is the difference between feedthrough and feedback capacitor? what is the meaning of this statement "CGD represents miller capacitance feedback while CDG represents miller capacitance feedback"
I have read about miller capacitance topic in odyseus's website but i dont understand what -G (nagative gain) mean. 180 phase shift??? How does this millter capacitance effect the input capacitance of a FET/transistor? thank you
To further amplify (sorry for the pun) on the post above, look at the schematic for the extra lumped capacitance added to the circuit. It will usually be across the input/output of one of the stages. The miller effect stated in the previous post is used to make the time constant larger than if the capacitance was across a lumped resistor.
my opinion is when a few limiting amplifier cascade together, the gain will increase from first stage to the last stage. As gain increase, the miller capacitance also increase according to formula cgd(1+A). This will form a even lower frequency pole as incresing stages, f=/2pi. RC. The output of the last stage will be the dominant pole or the firs
it could be because: at the cascoded node, you reduce the milled effect cap for the input. but at the same time you isolate the feedback resistor with that node. it means the output resistance is increase to (gm//gds). i am assuming the feedback resistor is much less than gm//gds.. then the bandwidth at the cascoded node will be reduced..
You are not doing this the standard way that most circuits work best at. You need to find which stage has the lowest pole frequency and add to the miller capacitance by putting the capacitor from base to collector on that stage. This will lower the dominant pole. I would guess that this is the second gain stage where you have the capacitor from
first - 200uV is exceptional! you can only hope that your chip has less than a few mV of ripple. try to look at it in terms of percent, and keep the percent lower than 1%... or 0.1% for extremely high accuracy. say your full scale voltage in lock is 0.5v, you can endure 5mV steady state ripple before you reach the 1% region. and if your f
The desirable property of common base is that the base-collector capacitance goes from the output to ground and does not cause a miller effect or feedback that causes oscillations. The collector-emitter capacitance is much smaller. In the early days of large junction areas the common base circuit was commonly used at VHF. Modern (...)
Hi zhi_yi, I hope the following helps. Voltage Divider Bias - commonly used for biasing BJT single transistor amplifier, especially in a common-emitter configuration to provide for medium current gain and medium current gain. - bias the base voltage so that you have a DC level for the input signal (AC) to swing. - the resistors are selecte
I have designed a 6bit Pipelined ADC. However, I got some problem when i design the reference voltage circuit. Because I have no output pad for VREFP(1.75V) and VREFN (1.25V) , so I add a large cap (about 400pF) on chip. I wonder which kind of OPAMP I should use. For a one stage( folded) opamp, the large cap let the bandwidth very low ( about 1K
Cgd4 does not need to be accounted for the pole at Cgs3 and Cgs4, this is because a pole-zero doublet happens before the Cgd4 miller cap can take effect.
G35, yes, voltage spike on the drain can effect the gate voltage. The reason for this is the gate-drain (miller) capacitance of the FET. Have you tried to limit the spikes on the drain by using a snubber circuit from drain to source? The snubber would either be a RC or a RC+diode circuit. Before putting anything else around the circuit I would
I'm using miller capacitance sample and hold cirucit. For an 8-bit resolution my sample circuit must be able to detect and hold at least 12mV. Right now I'm only able to make the resolution to 0.2V @ 200mV. Can I get ant suggestion of how can i achive my targeted resolution. Thanks in Advance. Best Regards Syukri
Well the thought of adopting GM-filter is a good choice and the other sugestion of using miller cap is also suggestion is to go for gm-filter.u can use the o/p impedance of the mosfets for this cause.if that is not enough u can use cascoding techniques to increase the R and decrease the C .
...if anything, at the moment of the collector voltage increase, via the miller capacitance, the base of the transistor would see a current injection, which should turn the transistor on more. But this current overshoot indicates an opposite transient. When we increase collector voltage: Collector-Base junction
I have tried to design some distributed amplifier using the book by Virdee. I do have design examples using ADS. Let me try to find it. I have done it for few years. In Virdee's book they use a chip FET and use wire bound as inductors. I dont know this approach will be good up to 10 GHz or not. I would think that it is better if you can design it a
It can also increase the bandwidth, due to reducig the miller capacitance. of the commen emitter/source amplifier.
Like to other two contributors said, follow the design rules. Typical electrode configuration is C-E-B because you can put the base electrode over the outside isolation thus minimizing your collector-substrate capacitance. In addition, keeping the base electrode away from your collector will also eliminate fringing capacitance to the two electrod
Hi, I've found some papers. Mainly poor PSRR in ur ckt is result of miller capacitance influence. Change output ckt. Choose solution by yourself.
Hey As far as I know, this is the most common method and the aim is to use the miller capacitance to move the poles to stabilize the op amp. It is however not necessarily about the first and the second stage.
Hello everybody, I want to design sample and hold circuit using double sampling technique at 160MHz clock (320MS/s) and 70dB IMD. Here I choose the two-stage opamp, the schematics are here. (Two stage module and the double sampling). But slew rate and charge injection decrease the IMD sharply. I try to adjust the miller capacitance, but the effe
During oscillation startup, an inverter is basically operating as an amplifier with a dominant pole (due to miller capacitance). What would you expect for the total gain and phase shift when cascading these elements?
The attached graph is from W. Sansen book, page 189 and I am a bit confused, on one hand, the text in the book seems to suggest that the rule of thumb is that Cc should be smaller than CL, on the other hand, the gm chart seems to in
are you sure 10mA is enough,,,,remeber the miller capacitance too. try IRF.COM they are good with that sort of stuff
Thanks for the info. But I think we have to divide the "active clamp" into two categories: One is the gate active clamp to minimize the miller capacitance effect at turn off. The aim of this is to guarantee the OFF phase. Another is the voltage clamp. The aim of this is to limit the over-voltage during switching. I was asking about
I can't follow the explaination. Because the FET is driven from the gate, Cgd acts as a negative feedback (miller capacitance) that doesn't allow the gate voltage to fall below the threshold voltage in on state. Also the driver impedance and gate resistor dimensioning are against this possibility.
FIRST IT IS GATE-source capacitance that you charge up then when you reach VTH, then you charge up the miller capacitance = DG capacitance..... miller is the bigger one that you have to charge up. so its kind of complicated cuzz you first charge up one then the other one.
Hi, Usually a gate to source resistance is provided to prevent accidental turn-on due to noise or other factors or gate-to-drain internal capacitance (miller capacitance). Normally I use 1k and it always works fine. There is no need to put MOV across the resistance. Instead place a zener diode for providing gate-to-source protection from (...)
I think that is the miller capacitance, pushing back on a weak gate discharge. Perhaps you want more tail current. Or perhaps less finger count in the switching pairs. Current density tends to maximize speed. That CML gate is basically a tall cascode amplifier, high impedance at the drain. High Z tends to lower bandwid
One big problem is in how the output stage gain swings with headroom. Your final gain once you get into linear region is about nothing, so you need a high gain amplifier in front of it that then needs a pretty low frequency pole, that fights step response. One approach I have seen, is a split loop. One part high gain, low frequency (to get
In the CE amplifier the output voltage is in a inverse relation with the Ic current. When Ic increases when the input signal is swinging up the voltage across the collector resistor increases and as such the output voltage decreases (for the basic configuration Vout = Vcc-Ic*Rc). This is not the case for CC and CB. miller capacitance is due to a
A cascode stage is normally used at high (RF) frequencies to eliminate the miller capacitance effect between the transistor collector and base. The CB stage keeps the collector AC voltage of the CE stage near 0V so there is little AC negative feedback (feedback is undesirable) through the collector-base parasitic capacitance. A cascode amp (...)
I don't have experience with that kind of amplifier and also see it for the first time and obviously there is some math behind it. But here is what I can say by just looking at the schematic on slide 5 of your attachment. Obviously Cm1 serves as a miller capacitance to create the dominant pole. Cm2 with gm4 create another miller capacitor (...)
For analog applications, there are two options to speed up an opto-coupler - use it in current source mode, e.g. a cascode circuit or another means that creates a low (AC) load impedance, to overcome miller capacitance. - use it as a photo diode. In this case, you'll need the base terminal. Did you check, if the opto coupler pole is actually
I think this might be caused by the miller capacitance (the capacitance from gate to drain). When Vgs rises, it will tend to cause the Drain to rise until the point where the device turns on hard. Try a slower rise time on Vgs to see if that minimizes the spike.
Don't confuse cascade with cascode! Cascode is used to reduce miller capacitance and possibly increase gain and improve bandwidth. Cascade is simply putting one stage after another to increase gain. Keith.
Series gate resistance or an undersized predriver will give you a slew-rate-limited driver (miller capacitance*dV/dt vs available gate drive). Controlling slew rate internally is better than using a weak driver and counting on load capacitance to limit voltage edge rate, less board level loading variability in timing. You can also segment (...)
"Negative miller capacitance" aims at reducing the input capacitance.