Shown for the extended common mode input voltage range of the instrument amplifier circuit. The circuit A1, A2 and A3 can be precision instrument amplifier INA101 or INA102 constitution.
The figure shows, A1, A2 and A3 voltage magnification l00 times, then using precision amplifier unity gain amplifier INA105, connection to the amplifier inverting input, output follower mode, four resistors were about to internal circuit in parallel, thus obtained INA105 amplifier voltage amplification factor of 2 and a high input impedance (megohm). Total voltage of the circuit 200-fold magnification. Figure (b) is the internal structure of the INA101.