Analog electronic Circuit Basics-Integrated op amp

First, the main parameters of the integrated op amp

1.1 Open-loop differential mode voltage amplification factor AUO
AUO=20LG (uo/ui) DB
AUO is an important factor to determine the stability and precision of the op amp Circuit, hoping that the bigger the AUO the better.

1.2 Maximum output voltage Uopp
at a certain supply voltage, the integrated op-amp output voltage and input voltage maintain the maximum output voltage peak of an undistorted relationship. The value is smaller than the supply voltage. If the supply voltage is 15V, this value is about 12V.

1.3 Maximum differential mode input voltage Uidmax
The Uidmax is the maximum voltage that can be sustained between the inverting input and the co-phase input of the integrated op amp.

1.4 Maximum common-mode input voltage Uicmax
Uicmax is the maximum common-mode input voltage that can be sustained by an integrated op amp, exceeding this value, the common-mode rejection ratio is significantly reduced, and even the device is damaged.

1.5 differential-mode input resistor RID
the RID is the resistor value between the integrated op amp two inputs. The larger the RID, the better it marks the size of the integrated op-amp input to the differential-mode signal source to obtain the signal capability.

1.6 Output Resistance ro
ro refers to the output resistor that integrates the OP amp output stage. It reflects the capacity of the op-amp load.

1.7 Common-mode rejection ratio KCMRR
KCMRR refers to the ratio of the open-loop differential-mode input voltage magnification of the integrated op amp to the magnification of the co-mode input voltage, which is used to measure the symmetry of each parameter in the input stage. The larger the KCMRR, the greater the ability of the OP amp to suppress the common-mode signal.

second, the basic Operation Circuit

2.1 Proportions
(1) Inverse comparison example

When Rf=r1, Uo=-ui, called inverter

The function of R ' in figure is to eliminate the influence of the OP amp input bias current.


(2) Proportion of the same phase


In the diagram, R ' =r1| | RF, when the magnification is 1 o'clock, is called a voltage follower.

2.2 Addition
(1) Inverse-phase summation

When r1= r2= r3= RF, uo=-(U1+U2+U3)

(2) Summation of the same phase


2.3 Subtraction


2.4 Instrumentation Amplifiers

Characteristics:
① high input impedance;
② circuit has good symmetry, high common-mode rejection ratio and low drift.
③ gain adjustment is convenient, can realize program control;
The ④ resistor is tightly matched and can be integrated with the device.

2.5 points


2.6 Differential


2.7 logarithm

As the diode flows through the current is large, its volt-ampere characteristic and the ideal pn junction equation has a large deviation, and in the signal is small, it is difficult to meet the conditions of ud>>ut, so the circuit signal working range is small, in order to obtain a larger range of work, commonly used transistor diode form instead of VD.


2.8 Index

Analog electronic Circuit Basics-Integrated op amp