This is a design schematic circuit of the instrumentation amplifier using three op amp. With this schematic configuration, two of the three amplifiers (A1 and A2) gain the two input signals. The third amplifier, A3, is used to subtract the two gained input signals, thereby providing a single ended output. This circuit is using op amp MCP604 that is produces by Microchip, Inc. This is the figure of the design circuit.
Quad amplifiers are typically used in the three op-amp instrumentation amplifier discrete designs because of the matching qualities of amplifiers with the same silicon. In contrast to the two op-amp instrumentation amplifier, the input signal paths (at VIN+ and VIN-) are completely balanced. This is achieved by sending VIN+ and VIN- signals through the same number of amplifiers to the output and using a common gain resistor, RG. Since this input stage is balanced, common mode currents will not flow through RG. The common-mode rejection of this circuit is primarily dependent on the resistor matching around A3. When R1 = R2 = R3 = R4, common mode signals will be gained by a factor of one regardless of gain of the front end of the circuit. Consequently, large common mode signals can be handled at all gains as long as the signals stay within A1 and A2 input and output head room limitations. If the common mode errors of the input amplifiers track they will be cancelled by the output stage. [Schematic’s source: Microchip Technology, Inc].
Quad amplifiers are typically used in the three op-amp instrumentation amplifier discrete designs because of the matching qualities of amplifiers with the same silicon. In contrast to the two op-amp instrumentation amplifier, the input signal paths (at VIN+ and VIN-) are completely balanced. This is achieved by sending VIN+ and VIN- signals through the same number of amplifiers to the output and using a common gain resistor, RG. Since this input stage is balanced, common mode currents will not flow through RG. The common-mode rejection of this circuit is primarily dependent on the resistor matching around A3. When R1 = R2 = R3 = R4, common mode signals will be gained by a factor of one regardless of gain of the front end of the circuit. Consequently, large common mode signals can be handled at all gains as long as the signals stay within A1 and A2 input and output head room limitations. If the common mode errors of the input amplifiers track they will be cancelled by the output stage. [Schematic’s source: Microchip Technology, Inc].
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