testing for stability

[tvrgeek]

Just looking at the schematic. The same grid resistor for N and P outputs?

 

[Bensen]

Do you mean the gate stoppers?
Yes I know that in many design's with FET's the gatestoppers are selected this way to achieve an equal time constant between N and P channel.

Have you any idea for good the values for the 2SK1530 - 2SJ201 Fet's?

Greetz

 

[Bensen]

Can someone help me out with post number 83 from next thread? I'm wondering what causes the strange rising shape when using a 10kHz square wave.

First I thought that the input impdance of the amp was to low, I've tried putting a 22K resistor in series with the input and left the 10µF High pas cap out. All without succes.

http://www.diyaudio.com/forums/solid-state/198209-amp-design-subwoofer-9.html

Schematic post number63:
http://www.diyaudio.com/forums/solid-state/198209-amp-design-subwoofer-7.html

 

[maxpou]

Just looking at the schematic. The same grid resistor for N and P outputs?

Hi tvrgeek,
yes the grid resistors on output are the same value why it's not correct? Thank you! Maxpou

 

[maxpou]

Hi tvrgeek,
yes the grid resistors on output are the same value why it's not correct? Thank you! Maxpou

HI guys,
nobody can tell why? I'm not sure, but I think that because the input capacity of my mosfets are not the same and the same time the cutoff frequency. Maxpou

 

[cbdb]

I think its the resistor/input capacitance of the mosfets time constant that should be the same, and since n and p devices (even complimentary pairs) usually have different input capacitances the resistors should be different.

 

[maxpou]

I think its the resistor/input capacitance of the mosfets time constant that should be the same, and since n and p devices (even complimentary pairs) usually have different input capacitances the resistors should be different.

Hi cbdb,
thank you for reply, but how do I determine the good value? Maxpou

 

[maxpou]

Hi cbdb,
thank you for reply, but how do I determine the good value? Maxpou

HI guys,
somebody can help me? Thank you! maxpou

 

[Bensen]

Hi Maxpou,

Look at post nr41. I hope this can help you.

http://www.diyaudio.com/forums/solid-state/64685-complementary-diff-input-jfet-bjt-cascode-5.html


Greetz

 

[maxpou]

Hi Maxpou,

Look at post nr41. I hope this can help you.

http://www.diyaudio.com/forums/solid-state/64685-complementary-diff-input-jfet-bjt-cascode-5.html


Greetz

Thank you for reply Bensen,
I read quickly, I don't have much time for the moment but because I have a source follower as driver I can have the same value for grid resistor. You can confirm it? Thank you! Maxpou

 

[Bensen]

If grid resistor means the same as gatestopper, than Yes, I wouldn't know wy you couldn't use the same values for the N and P device.
80% if not more commercial amps have the same values.