I would like to ask you a question.
What are the advantages and disadvantages of the two types of cut-off frequency equalization of the following Mosfet output stage:
The cutoff frequency in the same in the two solutions.
Thanks
What are the advantages and disadvantages of the two types of cut-off frequency equalization of the following Mosfet output stage:
The cutoff frequency in the same in the two solutions.
Thanks
The question is, do you rely on the "cutoff" frequency to compensate the whole amplifier? Some designs do that although I don't really like that idea.
If not, the "cutoff" frequency should be way beyond the bandwidth of the amplifier. There should be little benefit to balance them.
Anyway, I would pick the 2nd one if let me choose.
If not, the "cutoff" frequency should be way beyond the bandwidth of the amplifier. There should be little benefit to balance them.
Anyway, I would pick the 2nd one if let me choose.
Hi G_M,
This thread may present much of the information you seem to be requesting about oscillation of the LAT MOSFET output stage...
Best, David
This thread may present much of the information you seem to be requesting about oscillation of the LAT MOSFET output stage...
Best, David
I think the first is likely to become an oscillator with a bit of wiring inductance here and there, so I'm with jxdking.
Thank you for the above replay. I can confirm that both solutions work properly; I have used them in a lot of designs.
Here the matter is not the oscillation but the equalization of the ft of Nmos and Pmos.
For my understanding in solution 1 the VAS needs to provide more current because the total capacity seen is greater, but, maybe, the current needs for Nmos and Pmos from the VAS is the same and so the circuit is more "balanced".
Solution 2 is more cheap because you do not need additional capacitors but, maybe, the circuit is less "balanced" because the Nmos require from VAS less current (because the Nmos Cin is smaller than the one of the Pmos) than from the Pmos
Here the matter is not the oscillation but the equalization of the ft of Nmos and Pmos.
For my understanding in solution 1 the VAS needs to provide more current because the total capacity seen is greater, but, maybe, the current needs for Nmos and Pmos from the VAS is the same and so the circuit is more "balanced".
Solution 2 is more cheap because you do not need additional capacitors but, maybe, the circuit is less "balanced" because the Nmos require from VAS less current (because the Nmos Cin is smaller than the one of the Pmos) than from the Pmos
Yes go for solution 2 ...You might consider to balance the gate capacitance,as the P-channel mosfet have significantly higher gate capacity then theitN-channel companion. without the capacitors(about 270pF) the amp will almost always be unstable....Best regards Frank
Sorry Giorgio,haven't read everything ...Yes but you don't need two caps on the 2sk1058 only between gate and source..This compensates for the fact that the P-Channel mosfet has a higher (gate-source) capacitance than do the N-Channel.It might oscillate if the caps are not fitted....greetings from northern italy,Frank