MOSFET latch not working.... WHY... comments fix it

263

03:57:55

This works on my RL breadboard but not here! What am I doing wrong? Pushing the button should turn on the LED.

My breadboard uses a vp2106 MOSFET:
*
*VP2106 MODEL
*
.MODEL VP2106   PMOS (LEVEL=3   RS=0.73            NSUB=5.0E14
+DELTA=0.1      KAPPA=0.0411    TPG=-1             CGDO=6.1716E-10
+RD=1.91        VTO=-2.30       VMAX=3.0E6         ETA=0.12098
+NFS=3.384E11   TOX=1.0E-7      LD=1.6980E-9       UO=865.45
+XJ=6.5E-7      THETA=4.063E-5  CGSO=9.10E-9       L=2.5E-6
+W=0.5E-2)
.ENDS

published 7 years ago

kiani

7 years ago

Think you need to set the FET parameters..

Tadmuck

7 years ago

Thanks for the idea. I tried changing that around based on the spice model, but it must be somethingpre fundemental. FYI: * *VP2106 MODEL * .MODEL VP2106 PMOS (LEVEL=3 RS=0.73 NSUB=5.0E14 +DELTA=0.1 KAPPA=0.0411 TPG=-1 CGDO=6.1716E-10 +RD=1.91 VTO=-2.30 VMAX=3.0E6 ETA=0.12098 +NFS=3.384E11 TOX=1.0E-7 LD=1.6980E-9 UO=865.45 +XJ=6.5E-7 THETA=4.063E-5 CGSO=9.10E-9 L=2.5E-6 +W=0.5E-2) .ENDS

2ctiby

7 years ago

Adjusted ... http://everycircuit.com/circuit/4655490725576704

hurz

7 years ago

The good thing, Messy saw its a P channel mosfet which has to be used. Congratulation! What messy did not saw, cuz he dont understand how components work together, its not just a latch, its a toggle switch. Check this http://everycircuit.com/circuit/5044153322045440 and get the bigger “adjusted“ picture. What a messy

Tadmuck

7 years ago

Thanks! Man, how did you figure out the transistor parameters? That’s a rhetorical question - I’m not asking you to recite the math here ;-). But I spent hours digging around trying to figure out the right values for KP and Lambda - LOL. I thought there was no way it would toggle in the app like it does on my breadboard, but you got it!

2ctiby

7 years ago

The OP stated that the button was meant to turn the latch on... no mention of a toggle ... If I had been told about a toggle, then I would have tried to do it without the Hurz alteration of the bjt parameters eg.. his Forward beta there of 350A/A etc... lol

2ctiby

7 years ago

Here is my adapted version for toggle... same pmos settings that I used before, and no hurz bjt messing ... http://everycircuit.com/circuit/6748994956165120

hurz

7 years ago

And again Mr @2cent tries to start a sidetrack. What a surprise “red herring“ cuz he did not know what a toggle is and how it works, or why he does not saw it from circuit reading. Anyway, let us ignore this messy. My BJT setup is a nice tune to come closer to a default BJT we all use, execpt Mr. messy. But Messy likes its PMOS messing with 130nano Ohm Rdson. LOL Messy is action

hurz

7 years ago

@Tadmuck, you are welcome! Yeah, VP2106 semes to be close to BS170 NMOS, but the complement in P channel mosfet. Both are in TO92 package and Vth and Rdson are close in absolut value.

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