Tl331 and suitable resistors value to form a square pulse out of it

 I want to use/cut the output signal characterized as+-10V, 31 kHz, and dutyfactor  0.5 +-5-10% from the seconary side/ secondary coil of a Flyback topologie as a  5V controlsignal.The pulsewidth of the 5V control signal variable pulsewidth will be utilized for regulating/controling a servosystem consisting of CMOS. Today I use Zenerdiods( the last 5,1V)/ to cut the split of the output signal above down to around 5-6 V,but thereI get a no desireble minus voltage of 0.6V from the zener.
I want to use  an op. amp instead and think the TL331Q would do...Please give me a suggested connection scheme with suitable resistor value, and how I handle the earth and IN' and IN- . It's  fed from a +5V supply LP2985.