Hi, I am injecting a 20V, 400Hz Square Wave into the below circuit, but after it is stepped down through the OP AMP to a theoretical 20mV Square Wave, it is incredibly noisy. The circuit uses a Pi filter with a ferrite bead (P/N: HI1206T500R-10) with impedance of 50 ohms at 100MHz. The circuit also implements an inverting op amp to with a gain of -0.002. The Toff also appears to have a steeper rise time than the Ton and suspect this to be from capacitance. After searching the forums, I found a suggestion for using a Zener diode to help remove some of the spikes, but wanted to get input specific to my problem. I do have 0.1uF caps across the +15V and the -15V to ground. Thanks guys!