[sdiy] Latch-up question

[Theo]

Just a little addition.
To see how they behaved I tried to make TL07x latch-up but failed.
Later noticed in the data sheet the TL08x and TL07x indeed only phase
reverse but don't latch-up.
Normal operation is restored as soon the inputs conditions are back within
limits.

Didn't try this but maybe the TL07x could be used as a window comparator
using the phase reversal as a feature?
Above a positive threshold the output in high, and below the negative input
limit the output also goes high.

Theo


----- Original Message -----
From: Roman Sowa <modular at go2.pl>
To: fmg <1984 at softhome.net>; <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, November 01, 2003 9:08 AM
Subject: Odp: [sdiy] Latch-up question


> yes, -11V should be safe, and I bet -12.5V would also
> work fine depending on IC used. That's assuming TL is
> powered from +whatever, -15V.
> Phase reversal starts when input stage is not properly
> biased. Having p-FET inputs, TL07x needs couple of
> volts above -Vss to bias them. OTOH just because
> of that there's no limit for upper voltage.
> And since datasheet specifies differential input voltage
> at +/-30V (which means there are no clamping diodes)
>  TL should work fine even at (-) at +14.4V and (+) at -11V
>
> Roman
>
> ----- Original Message -----
> From: fmg <1984 at softhome.net>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, November 01, 2003 4:42 AM
> Subject: [sdiy] Latch-up question
>
>
> > Hi all
> >
> > I'm working in an adsr-r/env_gen and am facing the posibility
> > of phase-reversal issue in one (or two) of TL08x I included
> > in the design.
> >
> > What follows is an excerpt of National's AN447:
> >
> > >"In open-loop operation (i.e., no feedback from output to in-
> > >verting input, or, during any time that the opamp is slew-rate
> > >limited), taking the non-inverting input below the inverting
> > >input causes the output to slew toward the negative supply
> > >rail. If the voltage at the non-inverting input is more negative
> > >than the negative common-mode limit, the input stage ceas-
> > >es to function properly and the output swings to its positive
> > >limit. This apparent ``phase-reversal'' is temporary; bringing
> > >the non-inverting input back within the legal input common-
> > >mode range restores the part's normal operation."
> >
> > Now, wich is the "negative common-mode limit" ?
> >
> > In the TL081 datasheet is spec'ed:
> >
> > >Differential Input Voltage +/-30V
> > >
> > >Parameter           Condition       Min        Typ
> > >------------------------------------------------------------
> > >Input Common-Mode       Vs +/-15V     +/-11V    +15V/-12V
> > >Voltage Range
> >
> > Should I consider -11V the limit for the non-inverting input to
> > be in a safe area from latch-up?
> >
> > ...even if the inverting input is at a diode below Vdd (+14.4V) ?
> >
> > Are these assumptions wrong?
> >
> >
> > I'll appreciate any comments about.
> >
> > Thanks,
> >
> > Fabio Gonzalez
>