First, thank you for your attention. I'm trying to design an instrumentation amplifier for an EMG, supposedly, the one I'm trying to make has a gain of 41. I'm not that adept with spice design and I've been trying to get a cohesive results with I'm expecting, but I'm getting a gain of 10, but I think it is a default declaration from the program. Could someone lead me into the correct path? Any input is appreciated.

 

U1 and U2 need power from a & b, not gnd. You need to be sure that the inputs and outputs stay within the allowed
range (see common mode range and output ranges on the datasheet) For the LM741 I'd guess/remember
that you can't get very close to the V+ or V- power supply rails values for either input or output.

Figure staying 2 volts away -> with +9 -9 that means all the inputs need to be within +7 to -7 volts.

Clearly U1 with c at near ground is to close to the U1 negative supply which is ground.

 

The theoretical gain of you circuit is R1/RG+1 or 21.

Post you .asc file.

 

First, thank you for your attention. I'm trying to design an instrumentation amplifier for an EMG, supposedly, the one I'm trying to make has a gain of 41. I'm not that adept with spice design and I've been trying to get a cohesive results with I'm expecting, but I'm getting a gain of 10, but I think it is a default declaration from the program. Could someone lead me into the correct path? Any input is appreciated.

View attachment 305953

Why not use a real instrumentation amplifier chip?

 

I second eetech00"s suggestion.
An IC instrumentation amp will have greatly superior performance as compared to a roll-your-own design, primarily because of much better matching of the resistor values.