The OPAx990-Q1 uses a unique input architecture to eliminate the requirement for input protection diodes but still provides robust input protection under transient conditions. Figure 6-1 shows conventional input diode protection schemes that are activated by fast transient step responses and introduce signal distortion and settling time delays because of alternate current paths, as shown in Figure 6-2. For low-gain circuits, these fast-ramping input signals forward-bias back-to-back diodes, causing an increase in input current and resulting in extended settling time.

Figure 6-1 OPAx990-Q1 Input Protection Does Not Limit Differential Input Capability

Figure 6-2 Back-to-Back Diodes Create Settling Issues

The OPAx990-Q1 family of operational amplifiers provides a true high-impedance differential input capability for high-voltage applications using a patented input protection architecture that does not introduce additional signal distortion or delayed settling time, making the device an optimal op amp for multichannel, high-switched, input applications. The OPA990-Q1 tolerates a maximum differential swing (voltage between inverting and non-inverting pins of the op amp) of up to 40V, making the device an excellent choice for use as a comparator or in applications with fast-ramping input signals such as data-acquisition systems; for more information, see the MUX-Friendly Precision Operational Amplifiers application brief.