Hey people. I'm designing a circuit that requires some special characteristics, and I don't have much experience with this.
I need those characteristics:
Waveform: triangular and/or trapezoidal
Timing: ramps from 0 V to 40 V in 2 microseconds, held at 40 V for 2 microseconds, and then ramps back down to 0 V in 2 microseconds
Amplitude: 0 V to 40 V
Current: output around 2 A, with occasional peaks of 3–5 A
So far, I've defined the following:
Microcontroller: Pi Pico 2 (RP2040)
DAC: AD5428 in unipolar mode, with a reference voltage of –4.096 V (generated by an LM4040BIM3 and inverted using an ICL7660M)
Op-amp #1: connected directly to the AD5428 output, acting as a buffer (?)
Op-amp #2: connected to the output of the Op-amp #1, with a gain of 10 (to produce output from 0 V to 40 V)
Class AB amplifier for driving the load (capacitive load, ~200-400pf)
From what I've studied, I believe I need five transistors: two NPN, two PNP, and one NPN for the bias.
I have some questions:

1. Choosing the right components. I understand some of the theory (like gain-bandwidth product, slew rate, settling time for op-amps), but I'm still lost, here are so many options. I also have no clue which transistors are best suited for this application.
2. I need the components to be available in China, since I'm ordering the PCB with all components
3. I'm not sure if my logic is solid and functional. Does this signal "flow" I've designed make sense?

Could someone help guide me through this?
Thanks!

 

Why do you need 5A output? It only takes 8mA to charge 400pF to 40V in 2us.
It would be simpler just to charge and discharge the capacitor with a constant current source.

 

The power capability specified versus the load characteristic described does seem a bit confusing.
I suspect that we do not have all of the information.