Bootstrap protection diodes

[moffy]

Bootstraping protection diodes for sensitive circuits.

I was looking through an excellent book on low leakage input amp in which the author spent a lot of time analyzing the op amp and then placed a couple of 1N914 diodes to the +/- 15v supplies without any analysis. He had an error budget of 10pA which can easily be swamped by the diodes especially at higher temps.
Also there is the common case of oscilloscope probe amplifiers, the protection diodes have to be taken into account especially their non linear capacitance with voltage. So I thought I would use a simple LTSpice circuit to illustrate.
In one circuit the protection diodes are boostraped by and NPN and PNP voltage follower. In the other case they aren't. A single 5k resistor is in series.A 1Mhz 10vp-p tone is applied in both cases.

Bootstrapped:
1.Current: 240na p-p
2.Harmonic distortion: 97 db down

Non Bootstrapped:
1.Current: 110ua p-p
2.Harmonic distortion: 70db down

With some matching between the diodes it would be possible to get say a 10 to 1 improvement in leakage current.