I came across a schematic of a buffer amplifier utilizing a p-channel fet as input. It is from a sweep oscillator generating a ramp voltage by charging C3 and C4 with a constant current, (current source is not shown, Q2 just acts as a switch or buffer). Now as the voltage rises linearly across C3 or C4 the gate of the p-channel fet Q3 picks it up and the amplifies it from -5 to 5 volts in conjunction with Q1. So what I'm trying to accomplish is to derive an expression of the output voltage (-5 to 5) as a function of the input voltage at the gate Q3. P channel fets always confused me.