Hi.hi,
Have you considered the output 'slew rate' required for the OPA, used for the LDO application.?
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Read thru this pdf and consider the relationship between GBW and and Slew Rate SR.Hi.
No, I haven't. Does it relating to gain bandwidth?
Are you sure that we we are working with low frequency signal?.It seems to me that we are working with low frequency signals and so the bandwidth is not a problem.
I also read that a wide bandwidth will cause more noise generated by the op-amp since this noise is integrated overall its bandwidth.Using a low bandwidth amp leads to poor transient response plus high frequency noise on the output.
I only know that my input voltage is from 2 to 3.3V. How can I know that if there are high and low frequency components in that?Are you sure that we we are working with low frequency signal?.
What about digital circuit, RF circuit ect. Thous circuit are also supply from voltage regulators. But as with all digital circuits, the supply current is drawn in very short spikes on the clock edges, and if I/O lines are switching, the spikes will be even higher. So digital circuit will cause current pulses is drawn from our LDO reg. And this is why our LDO need to be fast.
But what about rise time ?I still can't see the relation between slew rate and gain bandwidth product. They are two different concepts and seems there is no relation.
How to know that the intersection point of closed-loop gain and open-loop gain curves is f-3dB?Another indicator of op amp speed is the small-signal slew rate. This parameter is tied to the frequency corner where the closed-loop gain meets the amplifier open-loop gain curve. This point is shown in Figure 2.
But Vout is not 0V. Vout = Iout * ZloadFrom the first link:
Vout = Iout1/(2πCc*f)
How can you know that the voltage at the output of transconductance stage is 0V?
Because this is how we define our corner frequency.Also from that link:
Another indicator of op amp speed is the small-signal slew rate. This parameter is tied to the frequency corner where the closed-loop gain meets the amplifier open-loop gain curve. This point is shown in Figure 2.
How to know that the intersection point of closed-loop gain and open-loop gain curves is f-3dB?
It represents the gain of amplifier with frequencies when when no feedback is used.Do you know what Open loop gain vs frequency represent?
It is the gain of amplifier with feedback.And what Closed loop gain is?
Misleading? Maybe for the beginners. Because we always using asymptotic approximation when we draw gain vs frequency.Thanks. I think the picture in the post #13 is a bit misleading.
fc = -3dB point should be the point in which closed-loop gain drops to 37dB not 40dB as in the figure.
by Jake Hertz
by Jake Hertz