Ultrasound project - voltage/current, pulse width
No body answered, so after some research I will try to anwer it by myself :)

Practically all anwers on my questions can be found here:
http://www.ndt.net/article/0598/linas_eq/linas_eq.htm

and here:

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&amp;arnumber=1009345&amp;url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F58%2F21760%2F01009345.pdf%3Farnumber%3D1009345  ( you have to have access to IEEE library )

It is easier to make pulser with discharging capacitor because of output impedance. (good explanation in the first link). Scheme of simple capacitor discharge pulser circuit: 

Use of MAX1847 DC/DC is not good for this project. It can´t provide enough current. I´m going to make powering circuit with 230AC in and ~ 230DC out, only few parts are needed for this. It can look as this:


You can get negative rectifier output if you switch the +/- nodes.

I asked Microchip support about max short time current through theire pulsers, but they didn´t respond. But it is not so hard to find satisfactory MOSFET and driver for it. Harder is achievinng good rise and fall times (need of good MOSFET driver), but it should not be problem for times mentioned above.