Question for driving gate on mosfets

[filippos_ineglis]

Hello,
I'm trying to drive the gates of two N-mosfet for a class D amp(2N6661). I have Vrail(+)=70V connected to the drain of the high mosfet and Vrail(-)=-70V connected to the source of the low side mosfet(snapshot 1). To drive them fully on I have to apply +-90V to both gates. Is this normal? Is there any IC that does this thing?
There is also a simpler circuit of this mosfet(snapshot 2) and its DC Sweep simulation(snapshot 3).
There migth be some serious mistakes, they are my first tries.

 

[dick_freebird]

Each of the NMOSFETs wants to be driven, relative to
its source terminal, by about 10V (unless these are some
"logic level" FETs).

The low side FET wants -70 (off) and -60 (on). Its source
is pinned to the -70V rail.

The high side FET wants -70 (off) and +80 (on) because
the source is flying and the drain is pinned.

Driving it +/- 90V will work in simulation, but fry you up
a whole pan of crispy gate oxide in real life.

Now why you'd go and put 50 ohm series resistors and
use such a high supply, when you could get about the
same effective drive to the load using no 50 ohm
resistors and +/-12V or so, eludes me. Other than
maybe limiting the shoot-through current, which you
should do on the control (gate drive) end instead if
you wanted efficiency better than 20%.

 

[filippos_ineglis]

Hello,
thank you for your fast responce. I put the 50 ohm resistors to increase the damping factor, without taking into consideration the efficiency because I forgot it. I put a snapshot of a simpler circuit and a second snapshot of the output. It seems to work fine. The problem now is how to produce these voltages for gates. I will use an IC or BJT?