Op-amp that is operational amplifier, before we come to the point what is inverting amplifier we must have to know about fundamentals of Operation amplifier, characteristic of operational amplifier, application of operational amplifier.
What is op-amp?
The term operational amplifier (OP-AMP) refers to a class of high-gain DC coupled amplifiers with two inputs and a single output. The modern integrated circuit version is typified by the famous 741 op-amp. Some of the general characteristics of the IC version are:
• High gain, on the order of a million
• High input impedance, low output impedance
• Used with split supply, usually +/- 15V
• Used with feedback, with gain determined by the feedback network.
The operational amplifier (op-amp) was designed to perform mathematical operations like addition, subtraction, integration, differentiation in low voltage and current application. Although now superseded by the digital computer, op-amps are a common feature of modern analog electronics.
The OPAMP is constructed from four transistor stages, which include
1st stage : known as an input stage made up with dual input balanced output differential amplifier.
2nd stage : known as an gain stage made up with dual input unbalanced amplifier.
3rd stage : known as an level shifting stage made up with emitter follower circuit.
4th stage : known as an output stage made up with class b push pull amplifier.
The differential amplifier consists of a matched pair of bipolar transistors or FETs. The push-pull amplifier transmits a large current to the load and hence has a small output impedance.
The op-amp is a linear amplifier with Vout ∝ Vinp. The DC open-loop voltage gain of a typical op-amp is 103 to 106. The gain is so large that most often feedback is used to obtain a specific transfer function and control the stability.
Cheap IC versions of operational amplifiers are readily available, making their use popular in any analog circuit. The cheap models operate from DC to about 20 kHz, while the high-performance models operate up to 50 MHz. A popular device is the 741 op-amp. It is usually available as an IC in an 8-pin dual, in-line package (DIP).
The schematic diagram for an inverting amplifier is shown in Figure (a). Observe that the offset and D.C. voltages have been left off of these circuits for simplicity. These connections are generally the same for all circuits using the same type of OP-AMP
Non-Inverting amplifier
The schematic diagram for a non-inverting amplifier shown in Figure (b) output of this circuit is in phase with the input. Notice that the input is applied to the non-inverting (+) input while the feedback is applied to the inverting (-) input.
What is op-amp?
The term operational amplifier (OP-AMP) refers to a class of high-gain DC coupled amplifiers with two inputs and a single output. The modern integrated circuit version is typified by the famous 741 op-amp. Some of the general characteristics of the IC version are:
• High gain, on the order of a million
• High input impedance, low output impedance
• Used with split supply, usually +/- 15V
• Used with feedback, with gain determined by the feedback network.
The operational amplifier (op-amp) was designed to perform mathematical operations like addition, subtraction, integration, differentiation in low voltage and current application. Although now superseded by the digital computer, op-amps are a common feature of modern analog electronics.
The OPAMP is constructed from four transistor stages, which include
1st stage : known as an input stage made up with dual input balanced output differential amplifier.
2nd stage : known as an gain stage made up with dual input unbalanced amplifier.
3rd stage : known as an level shifting stage made up with emitter follower circuit.
4th stage : known as an output stage made up with class b push pull amplifier.
The differential amplifier consists of a matched pair of bipolar transistors or FETs. The push-pull amplifier transmits a large current to the load and hence has a small output impedance.
The op-amp is a linear amplifier with Vout ∝ Vinp. The DC open-loop voltage gain of a typical op-amp is 103 to 106. The gain is so large that most often feedback is used to obtain a specific transfer function and control the stability.
Cheap IC versions of operational amplifiers are readily available, making their use popular in any analog circuit. The cheap models operate from DC to about 20 kHz, while the high-performance models operate up to 50 MHz. A popular device is the 741 op-amp. It is usually available as an IC in an 8-pin dual, in-line package (DIP).
The schematic diagram for an inverting amplifier is shown in Figure (a). Observe that the offset and D.C. voltages have been left off of these circuits for simplicity. These connections are generally the same for all circuits using the same type of OP-AMP
Non-Inverting amplifier
The schematic diagram for a non-inverting amplifier shown in Figure (b) output of this circuit is in phase with the input. Notice that the input is applied to the non-inverting (+) input while the feedback is applied to the inverting (-) input.
A resistor R1 is connected from the
inverting input to the common circuit between input and output. The
non-inverting input is always used when we do not want the signal to the
inverted.
Feedback is applied to inverting input through resistor Rf which
is connected to R1 and the OP-AMPs inverting input. The ratio
of these resistors (R1 and Rf) has an effect on the
circuit gain. Voltage gain can be calculated using the formula.
Av = (R1 + Rf) /
R1
Or Av = 1 + (Rf / R1)
This equation can be derived as follows:
Voltage across R1 is the input voltage
Vin = IR1
The output voltage is applied across the series combination
of R1 and Rf therefore,
Vout = voltage across R1 +
voltage across Rf
Vout = I.R1 + I.Rf
Vout = I (R1 + Rf)
Vout / Vin = (1(R1 +
Rf)/ IR1)
Av = (R1 + Rf) /
R1
Av = 1 + (Rf / R1)
As shown in
the figure if we change the value of Rf then voltage gain is also changed. If
we increase the value of Rf then gain will increase and vice versa. If we
increase the value of R1 then gain will be decrease.As shown in the figure
input waveform and output waveform are in phase with each other.
As shown in the figure AC input is connected to the non inverting terminal of the op-amp.
Here the value of the resistance is set in a such a way that gain is 3 as per theoratical calculation.
Here we can observed that output which is in orange colour is 3 times more than input which is in green.
We can also modified the circuit into voltage follower by setting the value of the feedback resistance to the zero and removing the resistance R1.
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