JAJSH88A April 2019 – June 2019 INA818
PRODUCTION DATA.
The INA818 is a monolithic, precision instrumentation amplifier incorporating a current-feedback input stage and a four-resistor difference amplifier output stage. The functional block diagram in the next section shows how the differential input voltage is buffered by transistors Q1 and Q2 and is forced across resistor RG, which causes a signal current to flow through resistors RG, R1, and R2. The output difference amplifier, A3, removes the common-mode component of the input signal and refers the output signal to the REF pin. The VBE and voltage drop across R1 and R2 produce output voltages on A1 and A2 that are approximately 0.8 V lower than the input voltages.
Each input is protected by two field-effect transistors (FETs) that provide a low series resistance under normal signal conditions, and preserve excellent noise performance. When excessive voltage is applied, these transistors limit input current to approximately 8 mA.