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Hi,
I am designing A two-stage OPAMP with double supply (vdd=2.5, vss=-2.5) using Cadence (Virtuoso),
when measuring the value of the Diff gain and CM gain measurement of the OP-AMP to measure the CMRR, is the common mode voltage in the input (vdd+vss/2)?
if yes this mean the DC voltage for...
Hi nitish5,
regarding your comment(As a part of convention, we usually go for (Vdd-Vss)/2 as a common mode point where one can do the measurement of the offset.)
the common mode point should be the midpoint (vdd+vss)/2 or (vdd-vss)/2?
Regards
Thank you for your comments,
Then, the measurement of input offset voltage value depends on the Common mode range, and the way of the measurement, the values in the previous pictures for the VCM and others are correct!! right? (No error in the connection) and the values.
Hi all,
I am designing A two-stage OPAMP with double supply (vdd=2.5, vss=-2.5) using Cadence (Virtuoso),
The question is, in the simulation to find the output offset voltage, for example, should the DC voltage be 2.5V or 5V as shown in the attached picture), and why?
The same question is for...
Absolutely, the following is understood (The phase of the loop gain must start at -180 deg for negative feedback (when the phase inversion within the loop is taken into account).
But, this is not understood (When the phase is 25 deg less than -360 deg - the PM is 25 deg).
Could you see the...
Hi LvW,
Thank you for the reply,
So, the rule of thumb is: if the negative sign in the loop is taken, then the rule is (180+ phase at gain 0dB), right?
if no, then the PM is from 0dB Y-axis of PM till to 0dB of the gain y-axis? right?
Thanks.
Thank you Dana for the explantation,
So, when we need to see the value of the phase margin we always start from the 0db (gain=1) Y-axis of the gain? but what about the Y-axis of the phase margin?
As shown in the attached picture, when they measure the phase margin, they start to find the 0db-...
Hi Dana,
Thanks for the reply,
Do you mean that in inverting AMP the Y-axis will start at 180 for phase margin, and 0 for non-inverting?
What if the Y-axis started with more than 180? as in the previous figure?
Please, how can I measure the value on the graph for phase margin if it started...
Hi all,
Why does the phase margin on the graph start from 0, sometimes from -180, sometimes +180? what is the reason? what is the starting value of the Y-axis in the Bode plot of the phase margin? any explanation, please?
Thanks.
Hi FvM,
Thank you for your reply,
Regarding (1) of your reply:
The RL voltage is defined as the given current, for example, if I= 1 mA from the current mirror the voltage will be 1V on the RL of 1K and so on.
Regarding: "apparently there's no CM feedback"
in the previously attached pictures...
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