Simple differential amplifier circuit

Operational amplifiers Al and A2 are connected in a noninverting configuration of their training sorties amplifier A3. The operational amplifier A3-one could call a subtractor circuit that converts the differential signal between the floating point X and Y in a single ended output voltage . Although not mandatory, amplifier A3 is usually used in unity gain and R4, R5, R6, and R7 are all equal. Joining-rejection of the amplifier A3 is a function of how the rate of R4: R5 R6 is the ratio: R7. For example, when using resistors with a tolerance of 0.1%, common mode rejection exceeds 60 dB. further improvement can be achieved by using a potentiometer (slightly higher than the value of R6) to R7.

The potentiometer can be adjusted for best common mode rejection. Input amplifiers Al and A2 will be some differential gain, but the common mode input voltage will gain experience unit. These tensions do not appear as differential signals to the input of amplifier A3, because when they appear at equal levels at both ends of R2-resistance, they are canceled. This type differential amplifier oflow level is widely used in signal processing. It is also useful for low frequency signals and routinely received from a sensor or thermocouple output. which are amplified and transmitted in a balanced mode. The amplifier is powered by supplies V ± 15. It is only necessary for zero input offset voltage of the output amplifier A3.

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