Input signal up to ±100V voltage follower (INA106)

For general integrated operational amplifiers, when the input signal is too large, the integrated chip may be damaged. Even if the integrated chip is not damaged, its working state has already entered the nonlinear region. The circuit shown in Figure (a) can still work normally when the input signal reaches ±100V, and the input voltage Vi is added to pin 3. This circuit is a common-phase input, and its amplification factor is 1. The integrated chip is INA106, which is a dedicated high-voltage input follower. No external resistor is required for general applications. The internal structure of the INA106 integrated chip is shown in the dotted box in Figure (b). Four metal film resistors are made on the operational amplifier chip at the same time. These four resistors are laser-corrected and have high precision, so the accuracy of the voltage amplification factor and the common-mode rejection ratio are very high. Because the metal film resistor has a good temperature coefficient, it can maintain high precision over the entire temperature range. As shown in Figure (b), a 1μF bypass capacitor should be connected to each of the positive and negative power supply terminals (pins 4 and 7) when in use, and the connection point should be as close to pins 4 and 7 as possible. Generally, pin 1 is grounded. If necessary, the offset voltage can be adjusted using pin 1. The circuit diagram is shown in Figure (c).