- output current up to 2A preferably 3A
- square wave's rise time (for a 10V square wave) to be ideally less than 50ns, preferably 10ns
10 to 50 nanoseconds requires from 35 to 7 MHz of bandwidth. That is not impossible; some function generators have class-ab output stages which achieve that level of performance, but they do it into a series terminated 50 ohm load for 100 ohms and 200 milliamps and not 6.6 ohms and 3 amps. So that leaves three options:
1. A heroic class-ab, or even class-b, current mode feedback amplifier should be feasible. Check out figure 12 of Linear Technology application note 21 for a lower current example. The problem will be finding fast high power PNP output transistors which are not as common as they used to be. 50 MHz ring emitter transistors might be sufficient at the lower end of the performance range but the higher end is going to require 200+ MHz transistors. Several will have to be used in parallel which is just as well because of the power dissipation requirements but the physical layout will be critical.
2. Open loop pulse amplifiers are feasible using a diode bridge to switch current sources, but the 2 to 3 amp requirement means it will draw a lot of power.
3. What I might try is paralleling like 4 x LT1210 integrated current feedback amplifiers in a symmetrical quad arrangement. If each drives 4 ohm ballast resistor, then that yields a 1 ohm output resistance.