What Is an Inverting Amplifier?
An operational amplifier in an electronic circuit has a non-inverting input terminal and an inverting input terminal. The polarity of the input terminal and the output terminal are the same polarity, which is the non-inverting amplifier, and the polarity of the input terminal and the opposite polarity of the output terminal are called inversion. Amplifier. The inverting amplifier circuit has a function of amplifying an input signal and inverting an output.
- As shown, the inverting amplifier circuit has a function of amplifying an input signal and inverting the output. "Inverted" means that the positive and negative signs are reversed. This amplifier uses negative feedback technology. The so-called negative feedback is to return a part of the output signal to the input. In the circuit shown in the figure, a connection method such as connecting (returning) the output Vout to the inverting input terminal (-) via R2 is negative feedback.
- The inverter is the basic gain stage in the CMOS circuit. It adopts a common source structure, and the load can be an active load or a current source.
- An integrated op amp, a 51K resistor, a 255K resistor, an 18K resistor, and an 82K resistor form an inverse proportional operational amplifier with partial positive feedback. The introduction of some positive feedback can achieve high gain amplification, and the specific structure is described as follows:
- 1. Form the basic negative feedback amplifier part: one end of the 51K resistor is connected to the input end, the other end is connected to the reverse input end of the op amp, one end of 255K resistor is connected to the reverse input end of the op amp, and the other end is connected to the output end of the op amp. One end of the 18K resistor is connected to the non-inverting input of the op amp, and the other end is grounded. The gain of the basic negative feedback amplifier section is 5.
- 2. Further constitute an inverse proportional operational amplifier with partial positive feedback: add an 82K positive feedback resistor to the basic negative feedback amplifier described above. One end of the resistor is connected to the non-inverting input of the op amp, and the other end is connected to the op amp. The output terminal is enough, and its positive feedback coefficient is K = 18 / (18 + 82) = 0.18. In this case, the input resistance is about 51K (If you think the input resistance is too large, you can replace 51K and 255K with 49.9K and 249K resistors, respectively. Resistance) The magnification is A / (1-A * K) = 5 /(1-5*0.18)=5/0.1=50.
Inverting amplifier integrator
- The resistance of the original inverting amplifier R 2 is replaced by a capacitor C 2. At this time, the relationship between the input signal Vi and the output signal V o forms an integral relationship.
Inverting amplifier differentiator
- Replace the resistance of the original inverting amplifier R 1 with an electric capacitor C. At this time, the relationship between the input signal V i and the output signal V o becomes a differential relationship.
Inverting Amplifier Adder
- If the inverting amplifier is slightly changed, the relationship between the input signal and the output signal V o at this time, if R 1 = R 2 = R 3 = ... = R n = R f , it can be simplified to V o =-( V 1 + V 2 + V 3 + ... + V n ), forming an additive relationship. [2]