Problems with a Jung regulator

[Gluca]

Folks,

I need to build a pair of Jungs regulator (positive V and negative V) for my DAC but I am having problems with the spice simulations I am running before the soldering the proto. I will use OPA37 and not LT1115 (I had no model for the BB opamp).

The positive reg seems to be OK:
R3 is a 1K pot and I can set the output voltage down to +12V (larger value will allow to go down to the minimum possible set by the zener). R7 represent the load.

pos reg

The negative reg doesn't work. SOOB. I am quite a newbie with solid state. I can't find out whats wrong there.

neg reg


Thanks
Gianluca

 

[mjf]

hello.
perhaps try r2-r3 connect to the negative rails (and not to ground).
greetings..............

 

[Gluca]

Hum ... no. That would not work. The circuit seems to regulate with no problem if the zener is connected (via the R4 resistor) before the mosfet drain (ie at the raw supply).

Thanks
Gianluca

 

[mjf]

hello.
perhaps reverse the polarity of the signalgenerator.......
and/or sine(-35 1 10).
greetings...............

 

[nvshier]

connect a 10k resistor between S and D of IRF