The integrated op amp is a multi-stage circuit with extremely complex interior. Usually, in circuit design, we only need to master the relevant characteristics of the integrated op amp. DC-DC isolation type The specific internal circuit does not need to be overly considered. To learn and understand the characteristics of the integrated op amp, we can pass Analysis of some typical op amp circuits to understand their relative characteristics.
Before analyzing the op amp circuit, we need to understand two important concepts: virtual short and virtual off.
Imaginary concept:
When the ideal op amp circuit works normally, the potential V+ of the non-inverting terminal is approximately equal to the V- of the reverse terminal, but in fact the two ends are not short-circuited, so this relationship is called virtual short. The concept of virtual ground can be further introduced. As shown in the figure, the same-direction end is grounded, resulting in the reverse end having ground potential, but the direction end is not grounded, which is the virtual ground.
The concept of false break:
When the ideal op amp circuit works normally, the input resistance is infinite, and the input current is approximately 0. There is no current on both ends, but the two inputs are actually connected, convert ethernet to wifi which is the concept of a virtual break. As shown in the figure below, according to the concept of virtual break, the current relationship can be calculated: I1=Ii+I2 I1≈I2(Ii≈0)
After understanding the two concepts of virtual short and virtual break, we will further understand the relevant characteristics of the integrated op amp through the op amp circuit.