44.6.10.8 High Gain Instrumentation Amplifier
In this mode, OPAMP0 and OPAMP1 are configured as non inverting amplifiers [Stage 1]. OPAMP2 is configured as difference amplifier[Stage 2]. Total gain of the instrumentation amplifier is product of gains of stage 1 and stage 2. The OPAMPCTRLx and RESCTRL registers can be configured as follows:
| MUXPOS | MUXNEG | RES1MUX | POTMUX | RES2VCC | RES2OUT | RES1EN | ANAOUT | |
|---|---|---|---|---|---|---|---|---|
| OPAMP0 | 0000 | 001 | 100 | 111 | 0 | 1 | 1 | 0 |
| OPAMP1 | 0000 | 001 | 100 | 111 | 0 | 1 | 1 | 0 |
| OPAMP2 | 1000 | 001 | 010 | 111 | 0 | 1 | 1 | 0 |
| RES1MUX | POTMUX | RES2OUT | RES1EN |
|---|---|---|---|
| 0 (DAC) | 111 | 1 | 1 |
| 1 (REFBUF) | 111 | 1 | 1 |
The resistor ladders associated with OPAMP0, OPAMP1, OPAMP2 and RESCTRL must be configured as follows in order to select the appropriate gain:
| OPAMPCTRL0.POTMUX | OPAMPCTRL1.POTMUX | STAGE 1 GAIN | OPAMPCTRL2.POTMUX | RESCTRL1.POTMUX | STAGE 2 GAIN |
|---|---|---|---|---|---|
| 0x7 | 0x7 | 16 | 0x7 | 0x7 | 15 |
| 0x6 | 0x6 | 8 | 0x6 | 0x6 | 7 |
| 0x5 | 0x5 | 5 + 1/3 | 0x5 | 0x5 | 4 + 1/3 |
| 0x4 | 0x4 | 4 | 0x4 | 0x4 | 3 |
| 0x3 | 0x3 | 2 + 2/3 | 0x3 | 0x3 | 1 + 2/3 |
| 0x2 | 0x2 | 2 | 0x2 | 0x2 | 1 |
| 0x1 | 0x1 | 1 + 1/3 | 0x1 | 0x1 | 1/3 |
| 0x0 | 0x0 | 1 + 1/7 | 0x0 | 0x0 | 1/7 |
The RES3TAP potentiometer can be selected as a positive input for the OPAMP2 and the resistor ladder can be connected to OA0OUT by setting the RESCTRL.RES2OUT bit in order to configure OPAMPs as a High Gain Instrumentation Amplifier.
