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Loop Gain Calculation

19 Threads found on edaboard.com: Loop Gain Calculation

calculation of input and output impedance using feedback technique

suppose any Voltage current feedback network is implemented and we have calculated its Aβ (loop gain) then how will i found its input /output impedance from this expression . Figure is given below for a reference I have calculated Aβ as -gm1 ro1 {Rs gm / (1+ gm Rs)} I can confirm your loop gain expres

Calculation of Gain and Bandwidth for Differential Amplifier

Hello everyone, I have to design a fully differential amplifier design. I have been given the following specs, How to calculate the gain and bandwidth of the amplifier: The given specs are: 1)Close loop gain 2)Max Input Step 3)Max gain Error 4)Max Settling error 5)Max Settling Time 6)PSR some other (...)

Feedback loop calculation for eight bucks in parallel

Hello The attached is a power supply involving eight current mode (CCM) bucks all in parallel, driving into the same load. Its easy to get the Feedback loop bode plots (& calculate gain and phase margin and crossover) for one buck supplying into one load, but how is it done for eight in parallel? Vin=28v vout = 1v5 iout = 136.8A total Eac

Colpitts's oscilator - frecuency

Its interesting, that oscillation will occur where the overall gain plus phase produces maximal feedback around the loop. For various reasons the transistor plus its parasitics may contribute some extra phase delay around the loop, which can pull the frequency. Another gremlin may be that the inductor has a core material that has a non (...)

Opamp error amplifier Theory and calculation

The error amp is only part of the overall open loop, as you know. But yes you need to find the transfer function of your one above, it is Zfb/Zin....use complex numbers to work it out. So you need the Power stage & modulator small signal trxfer function Then you also need the error amplifier small signal transfer function. Then multiply

Gain of TL431 needs to be found for feedback loop calculation

From the datasheet TL431, Fig 21, I see that dV(KA)/d(Vref)=1+(R1/R2); they are using an op-amp model for the gain. This equation is given in the Fig page 18. This would be the closed loop gain in a zener reference application but the application note in question specifically refers to the TL431 open loop (...)

colpitts oscillator circuit

Talking about an exact solution, you'll derive the circuit loop gain and determine the L range for that the Barkhausen oscillation condition can be fulfilled. Deriving the exact loop gain in a hand calculation is rather complex, even with a circuit simulator it's not really easy. A more practical (...)

Phase margin calculation in paper !!!

Hi all, I am studying the concept of phase margin. I understand the meaning but I have a question related to the calculation of the phase margin in paper. For example if I have a open loop system a(s) = 10 / ( (s+1) * (s+2) ), the phase margin in Matlab is approximately 55 degrees. So closed loop system is stable but I want to verify (...)

calculation of open loop dc gain with hspice

Hi. I designed a folded cascade Opamp with Hspice and I want to simulate it. I want to calculate dc open loop gain, Bandwidth, Phase margin. How can I do that? please help me. regard. A.Jafari

Difference in gain values

Hi When I simulated the open loop gain for a differential amplifier (using NMOS and PMOS transistors), the gain and output resistance values are much lower than hand calculation result. Why is there so much difference between the simulated result and calculated result/ Is it possible to manually edit model library file (...)

calculation of peak detector

The 0.65V voltage drop across D4 is reduced by the open-loop voltage gain of the opamp which is about 200,000 at very low frequencies and at DC. So a 2V input peak is reduced by (0.65V/200,000=) almost nothing so the output is 2V.

do i have to design the gain ang PM of a cmfb circuit?

hi all. do i have to design the gain ang PM of a cmfb circuit? what to do with stable open-loop but unstable closed-loop circuit? thanks in advance.

How to choose the GBW of audio amplifier

Hi all, I'm puzzled about how to choose the GBW of the pre-amplifier of audio amp, whose close loop gain is 1. By hand calculation, to keep close loop frequency response identical between 20Hz~20KHz, I think 600K GBW is enough, but the products of TI/NS have GBW more then 2MHz, some even reachs 10MHz. Thanks

BDC Motor Control - feedforward

Hello t_maggot, I think that you'll gain nothing, because the increase of current is the consequence of the control loop action: The speed decreses, so (SP-PV) increases commanding more tension (or more current if your power driver uses current feedback). I think that you must think in the delay introduced by the speed calculation from (...)

PSRR calculation question

It will be 50mV/20 at the output at that frequency where PSRR is 20. Calculate the input offset by dividing this by the closed-loop gain

Question on Phase Margin

-180 deg is same as 180 deg. It's 360 deg difference. Hi, I have some question here regarding phase margin calculation in feedback loop. Before this in my circuit design, i always see that my phase start either at 180 or 0 degree, so that at loop gain at unity i always get phase margin from 60 to 100 degree. But for this (...)

You need to do an open loop gain calculation and do a Bode plot. From this you can determine what changes you can make in the gains and pole-zero frequencies.

loop gain phase margin question

Hi mike_bihan, when a feedback circuit is analyzed, the load effect of the feedback network must be included in the calculation of the open loop response. The feedback network affects both the input and the output of the open loop transfer function. This is readily considered suppressing the feedback at the input for looking at its load (...)

what's the main input in the calculation of a loop gain?

as you know, when we calculate the loop gain we set the main input to zero at first.(P249 in the book "design of analog cmos integreated circuits" by Razavi). i want to calculate the loop gain in a switching power supply. the output voltage is constant. but what is the main input in the switching power supply system? the (...)