OPA445 is a high-voltage field-effect transistor input operational amplifier 2

power supply

OPA445 can operate on power supplies up to ± 45V or a total voltage of 90V, demonstrating excellent performance. Most characteristics remain unchanged throughout the entire operating voltage range. The typical characteristics show parameters that vary significantly with the operating voltage.diode

Some applications do not require equal positive and negative output voltage swings. The power supply voltage does not need to be equal. The voltage between OPA445 power sources is only 20 volts, and the maximum voltage between power sources can reach 90 volts. For example, the positive power supply can be set to 80V, the negative power supply to -10V, and vice versa.

input protection diode

The input of traditional FET input operational amplifiers should be protected against destructive currents that may flow when the gate of the input FET is forward biased to the substrate isolation diode. If the input voltage exceeds the power supply or there is an input voltage of VS=0V, this situation will occur. Protection can be easily achieved through resistors connected in series with the input. Be careful as the resistance in series with the input capacitor may affect stability. Many input signals have inherent current limitations; Therefore, it may not be necessary to restrict the resistor. diode

Fine tuning of bias voltage  diode

OPA445 provides bias voltage fine-tuning connections on pins 1 and 5. As shown in Figure 2, the offset voltage can be adjusted by connecting a potentiometer. This adjustment is only used to make the offset of the operational amplifier zero, not to adjust the system offset or the offset generated by the signal source. Zero position system offset will reduce the offset voltage drift behavior of operational amplifiers. Although it is impossible to predict the exact changes in drift, the impact is usually minimal.