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126 Threads found on Load Stability
If 0stability is desired one but conditional stability may be accepted in such cases.Unconditional stability must be valid up to Fmax of the transistor so no combination of load and/or source load will drift the LNA into oscillation regime. (...)
Before designing the feedback amplifier, you would make a specification. load impedance range, amplifier DC and AC characteristic (either gain versus frequency or characterized in time domain), intended accuracy. Presently you have a relative low, frequency independent loop gain (P controller). The gain won't suffice to cancel DC errors but can
Seems modeling problem if the datasheet says that the transistor is unconditional stable whatever the load is.
Do you mean that you want Vout=2*Vin? Or that you want an {error amp to output} gain that ensures stability given the op amp frequency response, output filter and feedback network details? You want high enough loop gain that load regulation is decent and PSRR is driven down to amplifier-internal limits, but not so high that you haven't gone t
Is the voltage ripple acceptable or causing any problems ? I suspect it is due to excessive phase shift in the LC filter with high Q resonance affecting the loop stability. What happens when you shunt the choke with a 5 Ohms? What happens if you apply a 1 A pulse load with 100mA steady load? Is it stable? Does it ring at the same (...)
Hello, Attached is a picture of an opamp with capacitive feedback. I think the load seen by the opamp is = Cf + C1 + diode ON resistance. Is this correct ? How do I determine the stability of this circuit in Cadence or any spice simulator ? Thanks.
I suggest you start injecting signals into an active load and monitor V,I for gain phase stability. You can get a sweep generator from Audacity, and use the audio inputs AC coupled as required to measure the response in time and frequency spectrum, or use scope for unity gain and measure phase margin, 130795
If I had to pick one or the other, I'd go with a harsh load step over the AP300 because you get to see both small and large signal response, and I've seen more "WTF?" involving the latter. Nothing against the AP300 or the need to diligently stabilize the design, just that small signal stability is not the end of it and a simple test method lets yo
Hello, We are using a PRM48BH480x250A00 power module (48Vin to 48Vout) to give a 1.5V, 95A output by using a VTM48EF015T115A00 ?electronic transformer? (NP/NS = 1/32) downstream of it. The actual load on the 1V5 rail is about 600 ASICs. Page 31 of the PRM48BH480x250A00 power module datasheet states that there are definite limits on the
i doubt it woudl be stabe with any output cap between 0 and many mega farads over the entire load range. Here is sim to look at to experiment a bit. (ltspice) You just need the transfer function of the power stage, error amplifier and modulator.....times them together, and get the gain and phase margin.
It doesn't appear to be based upon sound design principles, rather sort of trail and error approach. I suspect the output will be oscillatory under transient load testing. Maybe the user can enlighten us with a description of how it is supposed to work?
here is sim in free ltspice of linear around with compensation r and c and see its stability/response change. Do load stepping to see if you can get it to go unstable aswell. You kind of get the kind of value ranges of the compensation r and c which bring about a nice slow stable feedback loop....then you can check it with a gai
The stability of any feedback system for voltage and current is challenging from no load to full load or dynamic non-linear loads, lab supplies with these features tend to be more complex. This is similar to the feedback gain going from 0 to
If this is your 1st SMPS design, you might consider an inexpensive PC PSU. Historically older designs required 10% minimum load for stability. There are at least a dozen requirements to consider before you start a design.
CMFB effects on stability will result (1) from additional output load by CMFB inputs (probably negligible), and (2) CMFB output impedance change of control element input impedance, s. p. 18 of
1) Current regulation gain is too high and saturates to ground. The loop gain and phase margin is important for step load stability too. 2) If can create -2.0V say using some other source then you connect the R divider Vadj to drive the output to 0V. RED LEDs are good for 2.0V near 10~15mA and you might consider a charge pump inverter or some oth
A simple differential one-stage amp with constant current source and diode connection load should do. No stability problem.
There will be 2 speed control loops and 2 field control loops with a reference voltage for each to match the outputs with no load. When combining 2 voltage sources with and without a load, there be stability problems to resolve with no load and mismatched source impedance ; winding , cable resistance and field regulation (...)
You're right: this cascode circuit is not very temperature (nor supply voltage) stable. But at least Q1's Vc will stay 1*Vbe below Q2's Vb. The Figure 2.24 text just says the current stability referred to load changes is improved (compared to a simple constant current source). This is true, because the cascode transistor Q2 (in base mod
I have biased my circuit and i have check the stability. Now my next step is i want to match the 50 Ohm impedance to load impedance here in my case load is Transistor. So i have used the following methodology for my impedance i.e., first i have loaded the s parameters of a transistor then i have given the gain of a (...)
stability is criteria that begs a requirement for functional performance on overshoot, ripple, jitter etc. This is what drives the stability gain and phase margin. But also note that the margin changes with opearting conditions that affect SNR or load/capacity ratio or some other gain factor. If you know how to generate worst case (...)
Hi, I am designing a Flyback converter. I want to understand the inference of stability analysis related to power supply. 1.What is the meaning of a stable system? Stable means a step load won't cause lots of ringing or oscillation from a non-linear or capacitive load or any desired load it
3 GHz is quite high bandwidth. The question is about load capacitance and power consumption constraints. RFC with additional features could be a good choice - for the last 4 years it was the main way to performance improvements (check papers for 2011-2014). To ensure stability also feedforward compensation technique could be useful. With two stage
Why do you need a simulator, when you have good LEDs to use as a std load? Do you need production test jigs for nominal and worst case LED's with an active load? The main reason it wont simulate it due to the Shockley effect of your heat sink and since you haven't measure the junction temp yet using Vf, any simulation will be wrong u
You're right, you have a conditionally stable/unstable LNA. To have a greater confidence in stability when testing on the SA, don't just connect a 50Ohm termination to the input but also short and open. Additionally I test LNA stability on the SA also with a resonant filter (highly reactive load) at the input. If LNA doesn't show any strong (...)
Your simple buck regulators may be oscillating with insufficient load capacitance and low ESR for ripple or simply insufficient pre-load of 10% before the switch. Please advise if adding preload helps on stability and larger low ESR Cout Caps. - - - Updated - - - Your simple buck regulators may be oscilla
An oscillator has some quality factors mentioned below if I understood your question. -Drift : Temperature effect on oscillator frequency including self heating. -Pulling : Figure of stability : Function of load Variations on Oscillator Frequency -Pushing : Figure of stability : Function of Bias Variations on Oscillator Frequency These (...)
At very light loads / no load, you may not get enough o/p out of your aux winding to power the IC properly and it may be re-starting. Also the gain of the power circuit is different at no load and a slight amount of PWM will cause the o/p to go overvolts, stopping the PWM (and the aux output) until the Vo drifts back to just below the (...)
Because they never operate in linear small signal fashion, linear small signal analysis can't get a grip. Maybe if you created a state-space-average-model abstraction you could get some idea. But I'd settle (heh) for a transient load-step, line-step, inject-perturbation series of analyses and just eyeball it for whether it remains within regul
hi, Is it recommended to add/remove a capacitor at the output of a boost converter depending on the load , e.g, for low load single cap, for high load 1 + add 1 more.
Hello i'm planning on build a dc electronic load and i want to make the constant power and constant resistance modes analog so i can just put that in a feedback loop rather than constantly sampling -> making floating point calculations -> outputting through the dac so i need your help with an analog multiplier/divider circuit/IC whichever possi
A staircase waveform would add a load step excitation to the load variation and allow a visual stability check.
Why do I get so many smith charts in a single ( 4 circles starting from the centre?) graph while plotting L_stabcircle using smith chart(from the palette) in ADS? Which smith circle to choose for interpreting the stable region for output stability circle?
hi, i'm designing an integrated k/ka-band power amplifier with cadence virtuoso which looks similar to this one: 90974 in my case the load inductivities L1 of the cascode stage are about 100 pH. i simulated the s-parameter stabilityfactor kf. it is below 1 for a very wide frequency range from 20 GHz to 70 GHz. the m
Hey guys.I am doing a LDO stability analysis with corners. In most cases, the loop gain bode curves seem fine except @30mA load current, high temperature & strong device. The strange phenomenon is that "the loop gain phase margin curve" starts from 0 degree instead of 180 degree. The strange curve is attached in the "pic_stb". The red curve shows t
No load instability is common in SMPS and 10% pre-load activated by current sensor, may be needed. Overall open loop phase margin should be analyzed to improve stability to determine which capacitance and/or Input ESL affects the results. Alternatively put on the minimum load for stability (...)
89975 In the attached circuit is driving capacitance load and current of 5mA. sense and vdd_1v8 pins are shorted outside. To check stability and see loop gain and phase response for this circuit, where exactly i need to break loop?
Hi All, I measured the leg current of both legs at each step. one leg current is always higher than the other. And at full load 640W , the current difference between the two leg is 4A. Is this in allowable range??? How do you pack your windings? Can you give an illustration of the packing?
Good day, I am designing the front end for a 2m HAM radio. I have selected and bjt and simulated the load stability and found it to be unstable. I have chosen the method of a shunt resistor on the collector. The method requires me to plot conductance circles on the smith chart as close as possible to the plotted load (...)
Hi, I have been working on this project .... Let me describe the circuit so far... This is kind of load transient tester by linear... I am developing the similar electric load...but with capability of higher slew rate and high current at low voltage... at least 5, at 0.5 and current of 22 at the same condition... I have been ab
The most common reason to get instabilities at low loads is the transition from CCM to DCM. Did you consider the respective gain variation?
large bandwidth gives you a fast dynamic response that can gives you more tolerance for dynamic changes but the stability could become an issue. small bandwidth is usually more stable but due to the slow response the circuit may not be able to respond quickly to changes in the load current so you will get larger spikes in voltage due to step chang
Generators also have an enormous amount of inertia to handle the dynamic load of the grid (because usually weigh several hundreds tons of rotating mass). Greenies dream of shutting off the generators, and it would seem they have convinced the general stupid public that that is possible. The fact is that with windpower and other alt energy, the l
REturn Loss of Cap may affect stability. Can you scope current? 0.1Ω shunt? Type of ESR /SRF on cap affects ripple. Check specs and test. If you want to use an "active load " for testing , make a power transistor with heat sink and 0.01ohmshunt wire to ground. Then show I and V with scope as X & Y mode then you can simulate 10 ohm
There is a spurious resonance @ 9KHz with 25dB gain above normal at that point, so negative feedback becomes positive when Gain>1 & Phase Margin=0 what are the switching rates of SMPS1, SMPS2 and also load if known.? Pre-load may be necessary as well as lower ESR caps as suggested above on inputs of this loop {SMPS2}. > increased storage on
hi i would like to get any application notes to understand the stability issues for the following case. Dummy load and the controlling switch has to be connected at the output of a dc dc converter. When the load current is increased beyond a threshold limit, dummy load has to be disconnected. I (...)
Maybe you have damaged it with ESD or during soldering, or the supply has exceeded the 5.6 V maximum voltage. Check that everything is properly soldered. These IC's are pretty easy to use. Make sure however, that output capacitor is according to the datasheet requirements (although this is only for small signal stability) and that the load is betwe
Your posts are raising two questions: - conditions to achieve stability with capacitive load - required OP parameters for 100 mV AC @ 20 kHz I'll start with the second point. I can't follow your slew rate calculation, but you can easily calculate the required output current. I calculate about 0.25 A for 100 mV and 20 kHz, so it's obvious that
Temperature stability can be improved by proper use of PTC or NTC resistors. Power supply must be stabilized. Use decoupling interstage between oscillator and output to minimize influence of load variations on frequency.
In general yes, I'd expect it to remain stable. The RHP zero frequency should increase at light load, and as your controller starts operating in DCM, its gain should decrease. Those two things should only increase stability (unless the system was only conditionally stable). The only thing it could worsen is the damping of your LC, which might ca