This can be achieved by creating what is often termed a half supply rail. This is not always easy to achieve and therefore it is often convenient to use a single ended or single supply version of the electronic circuit design. Operational amplifier circuits are normally designed to operate from dual supplies, e.g. In this case the output impedance of the op amp will be low and therefore the largest impedance is likely to be that of the following stage. Similarly the output capacitor should be chosen so that it is able to pass the lowest frequencies needed for the system. The cut off point occurs at a frequency where the capacitive reactance is equal to the resistance. When inserting a resistor in this manner it should be remembered that the capacitor-resistor combination C1 / R3 forms a high pass filter with a cut-off frequency. Basic non-inverting operational amplifier circuit with capacitor coupled input If this resistor is not inserted the output of the operational amplifier will be driven into one of the voltage rails. The value of this may typically be 100kΩ or more. This can be achieved by inserting a high value resistor, R3 in the diagram, to ground as shown below. Where AC coupling is required it is necessary to ensure that the non-inverting has a DC path to earth for the very small input current that is needed to bias the input devices within the IC. In most cases it is possible to DC couple the circuit. This is a significant difference to the inverting configuration of an operational amplifier circuit which provided only a relatively low impedance dependent upon the value of the input resistor. The input impedance of this operational amplifier circuit may typically be well in excess of 10 7Ω.įor most circuit applications any loading effect of the circuit on previous stages can be completely ignored as it is so high, unless they are exceedingly sensitive. The impedance of the op amp non inverting circuit is particularly high. R1 = resistance of resistor to ground in ΩĪs an example, an amplifier requiring a gain of eleven could be built by making R2 47 k ohms and R1 4.7 k ohms. Hence the voltage gain of the circuit Av can be taken as: This means that Vin = Vout x R1 / (R1 + R2). The voltage at the inverting input is formed from a potential divider consisting of R1 and R2, and as the voltage at both inputs is the same, the voltage at the inverting input must be the same as that at the non-inverting input. If the output of the circuit remains within the supply rails of the amplifier, then the output voltage divided by the gain means that there is virtually no difference between the two inputs.Īs the input to the op-amp draws no current this means that the current flowing in the resistors R1 and R2 is the same. This arises from the fact that the gain of the amplifier is exceedingly high. The calculation hinges around the fact that the voltage at both inputs is the same. The gain of the non-inverting circuit for the operational amplifier is easy to determine. Basic non-inverting operational amplifier circuit Non-inverting amplifier gain It is the value of these two resistors that govern the gain of the operational amplifier circuit as they determine the level of feedback.
It has to be applied to the inverting input as it is negative feedback. However the feedback is taken from the output of the op-amp via a resistor to the inverting input of the operational amplifier where another resistor is taken to ground. In this way the signal at the output is not inverted when compared to the input.
In this electronic circuit design the signal is applied to the non-inverting input of the op-amp. The basic electronic circuit for the non-inverting operational amplifier is relatively straightforward. The op amp non-inverting amplifier circuit provides a high input impedance along with all the advantages gained from using an operational amplifier.Īlthough the basic non-inverting op amp circuit requires the same number electronic components as its inverting counterpart, it finds uses in applications where the high input impedance is of importance. The non-inverting amplifier configuration is one of the most popular and widely used forms of operational amplifier circuit and it is used in many electronic devices. Introduction Circuits summary Inverting amplifier Summing amplifier Non-inverting amplifier Variable gain amplifier High pass active filter Low pass active filter Bandpass filter Notch filter Comparator Schmitt trigger Multivibrator Bistable Integrator Differentiator Wien bridge oscillator Phase shift oscillator Op Amp Non-Inverting Amplifier: Operational Amplifier Circuit The op amp non-inverting amplifier circuit provides a high input impedance with all the other advantages associated with operational amplifiers.