60 Hz Notch filter design

Question

I am trying to replicate this circuit on LTSpice: 
 
 It is suppose to be a notch filter. I used the LT1178 op amp as the analog device product substitute which has the required bandwidth. However, my AC simulation does not show a 60Hz notch. I have attached my LTSpice model, and I have checked my circuit multiple times and I do not understand why I am not getting a 60Hz notch filter. The above image is generated from a filter design tool for a 60 Hz notch filter.

2450.60_notch.asc

dmercer · Accepted Answer

Hi: 
 This is a common rookie mistake. In the first schematic that you have tried to copy, the OP-amps are powered from dual + and - supplies. The positive input pins on the four op-amp that are connected to ground will be thus 1/2 way between the rails. In your LTspice simulation you have the four + inputs still connected to ground but are powering the op-amps from a single positive supply with the negative supply pin grounded. If you read the datasheet for the op-amp you are using you will probably see that the input common mode range does not include the negative supply pin. 
 If you wish to operate your circuit from a single positive supply then you need to generate a bias voltage at the middle of the power supply VCC/2 as it were. And connect the "grounded" components in the first schematic to that voltage. Mainly the + inputs on the op-amps but better to do all the connected components. In addition the input signal will need to be centered, ie. swing around this mid point of the power supply.)

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60 Hz Notch filter design