PMP Output Stage V2
Opposed to V1, this output stage utilizes conventional current mirrors (Q21,Q25 and Q24,Q28). As a consequence,  
the bias generator U1 needs temperature compensation by means of D6 and D7. Furthermore, the two stage  
approach of the clamp circuit is abandoned (first soft clipping, followed by hard clipping), instead, this one stands  
midway between soft and hard clipping. As a result, the clipped wave form is slightly convex, see fig.3, while version  
1 shows flat clipping, see fig. 2. At higher overdrive voltages, this version performs clearly better as the voltage drop  
of the current mirrors is about 7 times less, see concave fig. 4  vs flat fig. 5.
Also the value of gate stoppers is halved as well as the frequency compensation resistors R45 and R46.

Fig. 1 Ouput stage V2
Fig. 2 Flat clipping OPS-V1 at Vi = 1.6V
Fig. 3 Convex clipping OPS-V2 at Vi = 1.6V
Fig. 4 Concave clipping OPS-V1 at Vi = 2.5V
Fig. 4 Flat clipping OPS-V2 at Vi = 2.5V
To do:
1. further description OPS
2. gain and phase NFB loop
3. design rules
4. H(s)
Output Stage