Hi Scott, Happy to help! Your first figure shows a CR high pass filter where the two 10k resistors are in parallel which is equal to 5k. The resistor with a ? value will equivalently be in series with the 5k resistance. I recommend removing this resistor. R = 5k Since you said that the pulse width is around 100mS, I took that to mean that the pulse is around 10Hz. Rule of thumb for filter design is to put the cutoff frequency a decade before the signal frequency for highpass, or a decade after for low pass. Since you are designing a high pass filter, this means that the cutoff frequency should be ~1Hz. fc = 1Hz = 1/(2*pi*R*C) ~=~ C = 1/(2*pi*R*fc) = 1/(2*pi*5k*1Hz) = 31.8uF A 32uF cap should be fine. Make sure that the capacitor voltage level is capable of handling the DC that it will be coupling out. I attached a TINA schematic that may be helpful if you want to run some simulations. (Please visit the site to view this file)
↧