TTL(transistor transistor logic) to NIM (nuclear instrumentation module) circuit

hi friends, I'm doing university project concerning the converting the Transistor transistor logic(TTL) signal to Nuclear Instrumentation Module(NIM) signal. Here is my question,

1) i got the output square wave at the logic 0 recorded 600mv and logic 1 is -20mv. the result i wish to get is logic 0 record (range 1v to 0volt) and logic 1 is (-1.8v to -0.6v)...how to increase the gain of the level?by using operational amplifier? which type of op-amp i have to use?

2) Beside the addition of op-amp, what else i can do for my circuit in order to increase the level of the output?

3) the circuit i refer to was at the link below

lyoinfo.in2p3.fr/cms/cmsecal/TTL_NIM%20user%20manual_v10.pdf

4) Beside that, is it the capacitor and resistor which are in parallel with each other will influence the output?

5) which part of the circuit will play major in the translating the TTL to NIM?