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# Closed Loop Opamp Simulation

11 Threads found on edaboard.com: Closed Loop Opamp Simulation

## Fully differential Opamp CMFB - Strange behavior in closed loop

Hi All, I'm still on TT polyphase filter with current input and I saw a strange behavior in this structure when I'd simulated the CP1. My opamp is a classical 2 stages with a CMFB on activ load. In Open loop the gain is 58dB for a UGF at 27MHz and Phase margin is 45 degree. The stange behavior is the following: In the global strucure, when

## Hump in ac simulation of opamp while changing C values

Without schematic it's hard to say. If this plot shows sim results for closed loop operation this hump could be caused by low phase margin.

## Psrr simulation operational amplifier !

You need to do a simple ac simulation with power supply ac=1 and look on the output of closed loop opamp.

## GBW of an OpAmp simulation problem

How is the opamp supposed to be configured in application? On silicon, we inject a sine wave, and find the frequency in which its gain drops to half. The best method is to find the closed loop response, and get the product of the -3dB bandwidth and the DC gain. The problem with open loop for gbwp is that the response must (...)

## fully balanced opamp closed loop problem

The original TT-biquad consists of a non-inverting integrator (realized with a classical MILLER integrator and an inverter stage) and an inverting damped integrator (active low pass) - connected in a closed loop via a voltage divider. This topology can be realized with opamps (that's the classical solution) or with OTAs. I would recommend (...)

## Help me on Noise analysys in Spectre

construct a test bench which is closed loop and gain=1.add a vdc =0 as the input of the opamp. Spectre provide noise analysis. you could choose the differential output as the output pair. and input source as the noise source. After simulation you could print noise summary to see the total noise and the noise contribution (...)

## How to measure the GBW of a closed loop opamp?

lhlbluesky, GBW product is numerically equal to the frequency at which the open loop gain reduces to 1 (0dB). . closed loop bandwidth is usually deefined as the frequency at which the gain is down 3dB from the DC gain. The result is, the lower the closed loop gain, the higher the closed (...)

## How to make a ideal op-amp in HSPICE

Are you using the opamp in closed-loop ? This pseudo-device has infinite gain, I think, and will only simulate correctly in feedback configs, where the output controls the inputs so that there's zero voltage difference at the input. During transient simulation if there's any RC delay in the feedback path then the (...)

## help! an opamp with two stage(Ahjua compensation)

who can tell me why the simulation result is that as follows? It's closed loop opamp,with the ratio of cap being 2:1.I used two common mode feedback,cuz the opamp is two-stage.I use Ahjua compensation.The schemetic is as follows. The simulation is run several periods to make CM voltage (...)

## How to make opamp simulation of slew rate and fft

I'm not definitely aware of how to make the slew-rate simulation and fourier analysis. 1)Which method we should choose for slew-rate simulation, open loop or closed loop? If closed loop, should we connect it be voltage follower? And which point we should choose for the (...)

## The simulaiton of 2-order Low Pass Filter

Hello,I am designing a 2-order LPF,but I don't know how to do the simulation of AC characteristics for closed loop LPF and open loop LPF,can somebody help me? Thanks a lot!