I am trying to amplify the signal from a sensor that varies between 2mV-63mV. I need to amplify the signal about seven times. According to the datasheet the resistance I need to generate the gain is 7.2kohms. The way I have it connected does not change the gain regardless of the input voltage. Below the schematic photo.

 

The #1 issue is there are no bias return paths. Where is Ib going to go?

 

The #1 issue is there are no bias return paths. Where is Ib going to go?

What do you mean by lb. If you mean the amplified signal, it will go to the analog input of the teensy 3.2.

 

If you had looked at the data sheet you posted you would have seen that amp will not work with a single supple and an input connected to ground.
You either need a rail-rail type amp or dual power supplies.

 

cs: took a first order approach. I didn't look at the datasheet, Sorry. Here's http://www.analog.com/media/en/technical-documentation/data-sheets/AD8253.pdf#page=19 another discussion about Ib. This is usually true of any OP amp circuit.

Even with a rail to rail OP-amp, the rails may not be achievable. Generally, you would bias the output to 1/2 the supply voltage. Some REF pins need to be driven by a low Z source.

 

Since one input is ground, you don't need a differential instrumentation amplifier.
A rail-rail op amp configured for a non-inverting gain of 7 may be a better choice.