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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


     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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