Inverting op amp w/ a bias

Hi Kyle,

Take a look at this schematic and transfer function:

I would also recommend this resource: "Op Amps for Everyone - Design Reference"

Best Regards,
Chris

Thanks for the circuit Chris, but I'm looking for something where the gain is not applied to the Vbias if possible

Kyle,

Look through the "Op Amps for Everyone" resource for more circuit ideas.

I would recommend the following topologies as good alternatives:

1. Use R3 and R4 to attenuate Vbias, setting R4/(R3+R4) = (1 + R2/R1) would cancel out the gain OR
2. Use the resistor network (R1, R3, & R4) to scale the voltage at the inverting input. The transfer function for this is a little more complicated but can be solved for with nodal analysis.

Regards,
Chris

Kyle;

It is alot simpler and quicker to try circuit ideas using TINA-TI instead of breadboarding them!. Safer, too--- no smoke!

Chris,

i guess i should give you a better overall picture of what we are trying to do. We need to convert Diff to SE, then highpass filter (possibly with selectable freq points), selectable gain, and a bias for ADC interfacing. Our current design does all of these functions by using an INA, some tlv2381s, and a couple analog switches. The device draws 0.22mA at rest but increases to 1.5mA when a signal large enough to fill ADC input range is produced. This is a problem because our design constraints say that the circuit can't draw more than 0.3mA at any time other than start up. Any ideas? We are using a TLV2381 to do the Diff to SE conversion right now but are trying to find ways to reduce the IC count and use of our negative supply rail where possible to achieve the remaining steps needed.

thanks

kyle

Chris,

I can share more details offline. Cant share details over public forum. Can you post your email?

Thanks

Kyle