Looking for opamps with ability to tolerate input voltage above V+ ?

I have a board which is currently using several LT1491's, specifically for
their ability to tolerate up to 44 volts above V+ at the inputs. The down
side, is that they are expensive, and frequently out of stock. I'm curious
is anyone out there is familiar with a similar device which might be a bit
cheaper. I'm using this on heavy equipment with a 24v system. Commonly the
LT1491 has a V+ of 5v, however the inputs could momentarily be as high as
28v (due to miswires in electrical assembly).

Any ideas?

Thanks,

Chris

 

(setting a Fup2 s.e.c)

If the high input voltages are only due to miswires, you might as well
add protection circuitry to a more common, standard OP.

When looking for OPs that accept voltages significantly above V+, they
all are rather esoteric, expensive and/or hard to get.
The good ol' TL072, however, at least accepts input voltages /up to/ V+,
which might be sufficient in some cases.

 

I do have a 30v TVS (400Watt SMA package) protecting the LT1491 inputs from
ESD and short duration transients such as alternator noise. So I'm really
just trying to protect the inputs from 5 volts to the point where the TVS
turns on (around 33 volts.) Miswires in electrical assembly are
unfortunately frequent enough that I have to accommodate for them. They will
always be +24v to +28v depending on if the engine is running. The LT1491
works very well for this, since it's inputs are so robust, but at $4.25
each, I feel like I'm getting raped.

Any elegant ideas to protect a normal opamp while keeping the parts count
low?

 

Zener diodes??

 

Add a clamping diode from the input to the positive supply rail of the
op amp, and add a small resistor on the input signal to keep it from
frying the diode (assuming there isn't already one there for the
circuitry)

That sort of problem could be designed out.

 

["Followup-To:" header set to sci.electronics.]

the way I'm reading that, they just need to survive, they don't need to
function correctly in those conditions - right???

two:

build your own op-amps from discrete transistors.
pass labs have an article on their web site.

use series resistors (eg 1K) and shunt diodes to VCC or to a 3.9V zener,

 

in message

and might eliminate need for a fancy ESD protection device as well.