Hello out there,
I'm working on an electronics project to design active sEMG electrodes and I have designed my first pre-amp stage (so electrodes to instrumentation amplifier). I am using the double difference method in my INA setup and inputting a 750uV differential signal to the IA's. Each INA has a gain of 2 giving overall gain of 4. I am using the AD8237 INA's that are supposed to give a high CMRR, I am also driving the reference pin with a mid-supply voltage as shown in the schematic.
My question is in two parts;
1, I thought I understood gain, but this project has tested me, in the data sheet for the AD8237, they specify a gain of 2 is acheived with two 49.9kO resistors. I am confused by that figure, "2". Is that a decibel measurement i.e dB or is that a linear ratio of input to output voltage?
2, I have attached figures of my output via the Oscilloscope and have a measure for Vout, how do I then measure the CMRR of my configuration?
I'm working on an electronics project to design active sEMG electrodes and I have designed my first pre-amp stage (so electrodes to instrumentation amplifier). I am using the double difference method in my INA setup and inputting a 750uV differential signal to the IA's. Each INA has a gain of 2 giving overall gain of 4. I am using the AD8237 INA's that are supposed to give a high CMRR, I am also driving the reference pin with a mid-supply voltage as shown in the schematic.
My question is in two parts;
1, I thought I understood gain, but this project has tested me, in the data sheet for the AD8237, they specify a gain of 2 is acheived with two 49.9kO resistors. I am confused by that figure, "2". Is that a decibel measurement i.e dB or is that a linear ratio of input to output voltage?
2, I have attached figures of my output via the Oscilloscope and have a measure for Vout, how do I then measure the CMRR of my configuration?