ADA4522 opamp hangup

I was going to post the bootstrapped chopamp circuit, but it's just too awful. The high-voltage chopper amps are a vast improvement.

Yup, especially when you're facing large signals with fairly high slew rates. It's useful to put the op amp in a socket when debugging one of those bootstrap things. You also need quite a few spares. ;)

Cheers

Phil Hobbs

and adequate decoupling?

Oh yes, in this case PSRR and CMRRR do matter. I was thinking more about th e usual configuration of a HV chopper with fixed supply rails. Even if its PSRR is not stellar, you are on the safe side. Unless you make some blunder on the PS rails, that is.

I've seen a bunch of these PS bootstrap circuits in papers from the biomedi cal instrumentation community, for stuff like microelectrode instrumentatio n and electrochemistry. They have to deal with uncomfortably high source im pedances, but the signals are generally quite slow.

Cheers, Nikolai

We bootstrapped to get more voltage follower range, and bootstrapping also dramatically improves CMRR and PSRR, for slow unity-gain followers anyhow. Our problem was that we also needed speed, and the dynamics got messy.

Our other innovation was to change the specs of the instrument so we don't have to follow big inputs. Just one potential customer made us design for a big voltage range, and then he didn't buy any.

The good news is that if you ignore customers, eventually they go away. ;)

Cheers

Phil Hobbs