"Operational Amplifier Parameter Analysis and LTspice Application Simulation" Part 3 Chapter 2 Learning Operational Amplifier Indicators

常见泽1

"Operational Amplifier Parameter Analysis and LTspice Application Simulation" Part 3 Chapter 2 Learning Operational Amplifier Indicators [Copy link]

Chapter 2 mainly explains some op amp parameter analysis

The book explains it in detail, so you can read it carefully.

I also did some simple compilation based on some information on the Internet.

I have sorted out some parameters that are usually used.

Static characteristics:

(1) Input offset voltage

Definition: When the op amp is used in open loop, the DC voltage loaded between the two input terminals makes the amplifier DC output voltage be 0.

Nowadays, the input offset voltage of many op amps can be made very small.

Why is there input offset voltage Vos?

The op amp input stage, the differential amplifier circuit composed of BJT/CMOS, is theoretically completely symmetrical. However, due to process limitations, the mismatched input stage leads to input offset voltage.

(2) Common mode rejection ratio

CMRR: Common mode rejection ratio

What is common mode rejection ratio (CMRR)?

Differential signal amplification factor/common mode signal amplification factor

The larger the CMRR, the more effective it is in suppressing switching noise (common mode interference).

There is also an indicator called power supply rejection ratio

(3) Input Impedance

Input impedance refers to the impedance of the operational amplifier to the input signal. A higher input impedance can avoid interference with the input signal and improve the sensitivity and stability of the system.

Dynamic characteristics:

The impact on high frequencies is relatively large

(1) Slew rate

SR: Slew rate

What is SR?

The conversion rate of the op amp output voltage. Usually the unit is V/us

A certain signal needs to be protected quickly, and the slew rate will affect the delay of this signal.

(2) -3dB closed-loop bandwidth

-3dB bandwidth refers to the bandwidth when the op amp gain drops by 3dB, usually expressed in Hz. There is a relationship between -3dB bandwidth and unity gain bandwidth, that is, -3dB bandwidth is equal to the unity gain bandwidth multiplied by the ratio of the frequency when the open-loop gain drops by 3dB to the unity gain bandwidth.

The power half frequency point, 3db is also called the half-power point or cut-off power point. The power at this point is half of its total power.

okhxyyo

Reading summary: "Operational Amplifier Parameter Analysis and LTspice Application Simulation" https://en.eeworld.com/bbs/thread-1257415-1-1.html

zhaoyanhao

"Definition: When the op amp is used in an open loop, the DC voltage applied between the two input terminals makes the amplifier DC output voltage zero." Is this a typo?

常见泽1

zhaoyanhao published on 2023-10-30 08:56 "Definition: When the op amp is used in an open loop, the DC voltage loaded between the two input terminals makes the DC output voltage of the amplifier 0." This...

Open loop use

zhaoyanhao

Common Ze 1 posted on 2023-10-30 13:56 Open loop use

Yeah, I was wrong.