Ⅰ Introduction
Although there are many types of operational amplifiers, different amplifier circuits are suitable for interfacing with different types of sensors, but most complex amplifiers are built by combining operational amplifiers. In order to get good amplication effect, it is necessary to design the circuit of the amplifier. This paper will introduce 20 opamp formulas as a design reference.
Op Amp Formulas For Voltage Calculation
Catalog
Ⅱ Operational Amplifier Formulas
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
Figure 4. Voltage Subtractor, Differential Amplifier
Note: Amplify the voltage difference and suppress the common - mode voltage
Figure 5. Voltage Adder
Note: Summation of Adding Voltage Values
Figure 6. Low-pass Filter, Integrator
Note: Limit Signal Bandwidth
Figure 7. High-pass Filter, Differentiator
Note: Eliminate DC, Amplify AC Signal
Figure 8. Differential Amplifier
Note: Drive Differential Signal to Analog-to-Digital Converter From A Differential or Single-ended Signal Source
Figure 9. Instrumentation Amplifier
Note: Amplify the Low Level Difference Signal and Suppress the Common Mode Signal
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 Formula
Ohm's Law (DC circuit)
Figure 11. Closed-loop Frequency Response (voltage feedback amplifier)
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)
Add something, the op amp can be simply viewed as a high-gain direct-coupled voltage amplifying unit with one signal output port, a non-inverting input, and an inverting put, which belong to high-impedance inputs. So non-inverting amps, inverting amps, and differential amps can be made based on these amplifying units.
We should know the principle before calculations, the power supply mode of the op amp is divided into dual power supply and single power supply. For dual-supply op amps, the output can be varied across zero voltage and the output can be set to zero when the differential input voltage is zero. With a single-supply op amp, the output varies over a range of power and ground.
The output signal of the operational amplifier is proportional to the difference between the signal voltages of the two inputs. In the audio segment: output voltage = A0 (E1-E2), where A0 is the low-frequency open-loop gain , E1 is the input signal voltage of the non-inverting terminal, and E2 is the input signal voltage of the inverting terminal.