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Sep 19 2019

20 Formulas for Basic Configuration of Operational Amplifier Common Design

Although there are many types of amplifiers, different amplifiers are suitable for interfacing with different types of sensors, but most complex amplifiers are built by combining operational amplifiers. 

In almost cases today, op amps are configured in different ways using a feedback network to calculate the input signal. There are 20 formulas used to calculate.

Figure 1. Voltage Follower

Note: Buffer High Impedance Signal and Low Impedance Load


Figure 2. In-phase Op Amp

Note: In-phase Signal Amplification


Figure 3. Reversed-phase Op Amp

Note: Amplify and Invert Input


Voltage Subtractor, Differential Amplifier Circuit

Figure 4. Voltage Subtractor, Differential Amplifier

Note: Amplify the voltage difference and suppress the common - mode voltage


Voltage Adder circuit

Figure 5. Voltage Adder

Note: Summation of Adding Voltage Values


As a Low-pass Filter, Integrator

Figure 6. Low-pass Filter, Integrator

Note: Limit Signal Bandwidth


High-pass Filter, Differentiator.png

Figure 7. High-pass Filter, Differentiator

Note: Eliminate DC, Amplify AC Signal


Differential Amplifier

Figure 8. Differential Amplifier

Note: Drive Differential Signal to Analog-to-Digital Converter From A Differential or Single-ended Signal Source

 

Instrumentation Amplifier

Figure 9. Instrumentation Amplifier

Note: Amplify the Low Level Difference Signal and Suppress the Common Mode Signal

 

Single State Op Amp Noise

Figure 10. Single State Op Amp Noise

Note: RTO NOISE=NG×RTI NOISE

     RTI=Converted to the Input

RTO=Converted to the Output

 

Decibel Formula (equivalent impedance)

 

Johnson-Nyquist Noise

Johnson-Nyquist Noise Formula


 

Ohm's Law (DC circuit)

 

Closed-loop Frequency Response (voltage feedback amplifier)

Figure 11. Closed-loop Frequency Response (voltage feedback amplifier)

 

resistance formulas.png

Resistance Formulas

 

Reactance Formulas

 

Transformer (step-up or step-down ratio)

 

Impedance Formulas (in series)

Note: RL in series

RC in series

LC in series

RLC in series 

 

Voltage and Impedance Formulas (parallel connection)

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