kayaoo
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Thanks. I can not fully understand.The circuit is used for an RF receiver below 900MHz. I can understand that the R1 decreases the circuit's frequency and improves the noise of the node between R1 and C1. But what about the Vin_3V3 node?The reason of resistor is to increase the R1*C1 time constant, lowering in this way the decoupling frequency of the circuit.
Generally this approach is used in LNA design for improving IP3, and in Power Amplifier design to prevent low frequency oscillations.
In the zobel filter, the capacitor was used to cancel the inductance of the speaker.The resistor can broad the bandwidth. In my case, it will make sense if the VDD node's original impedance is inductive. But does a normal LDO or power supply output is inductive?I've seen it in audio amplifiers psu, i think it resembles a zobel filter but for the power supply and i have seen it make a difference in an ic amplifier (lm3886)
Speaker Zobel / Impedance Equalization Network Circuit Calculator
Alex
Thanks. It is meaningful. So the capacitor for the LDO load should has a ESR range.It will not work if too high or too low.[/COLOR]There is also an article
Maybe the resistor has something to do with the ESR of the capacitor...
Alex
Can you explain this technique in detail ??The reason of resistor is to increase the R1*C1 time constant, lowering in this way the decoupling frequency of the circuit.
Generally this approach is used in LNA design for improving IP3, and in Power Amplifier design to prevent low frequency oscillations.