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Please find the attached image. I'm measuring the IIP3 and my specification is 30dbm. I'm reaching the specification. But I'm seeing peaky behavior in the third order harmonic. Is this IIP3 curve plotted is correct or not? Can anybody answer this?
Thanks
Based on my experiments, I can say that for Sallen-key, the linearity increases with the gain of the opamp used in the loop. So its difficult for me to agree with you on that point.
And you have mentioned about ample feedback. Does that mean I should have large phase margin?
Hi all,
I'm designing a filter for which the linearity is of higher importance. I noticed that linearity will increase if I have higher current in my circuit legs.
But I wanted to know on what all parameters the linearity is mainly dependent?
Is it dependent on gain and phase margin of the...
Hello all,
I'm just analyzing the differential difference amplifier(DDA) circuits and thought DDA will be the good fit for the active filter designs. But I'm not clear with the advantages that I will get with DDAs. Can anybody explain what are the advantages of DDA over OPAMPs?
Yes. I understand. But I cannot afford to use Inductor in my design because of area constraints. Do you suggest any other topology for 10MHz cutoff frequency? I went through quite a lot of articles and concluded that Sallen-Key is the best topology for high frequency application. I cannot go...
I have one more concern in designing the opamp. If the cutoff frequency of my filter is 1MHz, then should I design an opamp which is GBW as 100*cutoff frequency?
Hello All,
I'm designing a Sallen-Key low pass filter with a cut-off frequency as 10MHz. For this filter, I'm designing an OPAMP which is single stage folded cascode (as folded cascode is preferred for the unity gain configuration and I need this unity gain configuration for the Sallen-key)...
Hey Ali,
If I make the circuit to work in Unity gain feedback mode, then we dont have the gain dependency in the transfer function right? As my specification for the filter is 0dB, I can operate in unity feedback.
So all I have to worry about is, if I'm designing a low pass filter with cutoff...
Hey Ali,
Thanks. This is what I was looking for. Yes. I have power and area constraints. So as you suggested, going for Sallen-key will be suitable for my design. Any idea on how much should be the open loop gain for the OPAMPS for this topology? Will a single stage folded cascode with 60dB...
Hello,
I will implement the on chip tuning later.For the initial tape-out, I will go for off-chip tuning.
First I have to stick to the topology. I have decided to stick to Sallen-key topology with single ended opamp and supply voltage as 1.8V in .18u. Is this feasible?
Hello,
I'm planning to design the opamp to work in this frequency range. To make an opamp to work from 1M to 10M will not be issue i guess. My question is whether Sallen-key topology can work in this frequency range ? Or should I go with bi-quad?
In Sallen-key I can use only one opamp.
Hello all,
I'm starting an active filter design with in .18u technology. Its a low pass butterworth approximation with 0dB gain and with frequency tuning capability. I'm confused about selecting the topology for the implementation. There are topologies like Sallen–Key topology,Tow-Thomas...
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