High Voltage Op Amps

[JoeyG]

Why would you use a high voltage Op Amp instead of resistor dividers  etc.?

Higher input impedance ?    Faster  rise time?   Other

[David Hess]

Some applications require or are made simpler with a high voltage operational amplifier.  It is possible to bootstrap a low voltage operational amplifier for higher voltage operation or use level shifters but this can get complicated fast.

[coppercone2]

for stuff like electrometers, maybe

when you come across the need it will be obvious

when you experiment with modified op-amp circuits, you will likely experience frustration. I recommend just getting HV op-amps if you can. The modification of a LV op amp to HV op amp is like something that you should be expect to be paid for, since in most cases it just a BOM cost reduction based on opportunity for certain parts and volumes of scale etc, unless you need something specific, which can be effected by the modification you made.

[danieljfarrell]

I was looking into high voltage opamps to make a simulated inductor / gyrator for an audio amplifier. But far to expensive for the ones I need.

[Kleinstein]

A divider is not an alternative to an amplifier, it is more like the opposite direction. It is only a few special cases that a divider directly at the input may allow to get away without a high voltage amplifier (more like a buffer).

Operational amplifier are conventient building blocks and sometimes the more normal models for a 30-40V supply are not enough. It is possibly to build an amplifier from separate parts (this may include a more more normal OP-amp, but could also be fully discrete). For higher voltage this is sometimes done, as the choice of high voltage OP-amps is limited and power dissipation can become an issue. So the normal SO8 or similar case may not be such a good option.

[Terry Bites]

There is a cheap way to get an HV opamp.  See https://www.digikey.co.uk/en/articles/how-to-solve-analog-high-voltage-delivery-challenges

[Kleinstein]

The depeletion mode mosfets are a neat way for bootstrapping, but this only works easy for a buffer and without much capacitive load.

[mawyatt]

I was looking into high voltage opamps to make a simulated inductor / gyrator for an audio amplifier. But far to expensive for the ones I need.

The TI OPA462 might be worth considering, not too expensive (~$20) and somewhat available. We recently selected and used ~300 of these in an experimental phased array controller (basically a 16 bit 256 channel HV AWG), and they have some "additional" features like Overload indication and Enable.

https://www.ti.com/lit/ds/symlink/opa462.pdf

Best,

[Zero999]

When a high output voltage is required.

It's also possible to add components around an existing op-amp to increase the output voltage and current.