What is an IC 741 Op Amp : Pin Diagram & Its Working

The short form of the operational amplifier is op-amp, which is one kind of solid-state IC. The first operational amplifier is designed by Fairchild Semiconductors in the year 1963. It is the basic building block of analog electronic circuits that accomplish different types of analog signal processing tasks. These ICs use exterior feedback to regulate their functions and these components are used as a multipurpose device in various electronic instruments. It consists of two inputs and two outputs, namely inverting and non inverting terminals. This IC 741 Op Amp is most commonly used in various electrical and electronic circuits. The main intention of this 741 op-amp is to strengthen AC & DC signals and for mathematical operations. Let us be clear about this 741 Op Amp by knowing its properties, pin diagram, specifications, and related concepts.

What is IC 741 Op Amp?

The term operational amplifier is the full form of an op-amp and it is one kind of IC (integrated circuits). An op-amp is a DC-coupled high gain voltage amplifier with a differential i/p and a single o/p. In this structure, an operational amplifier generates an o/p potential that is usually many times larger than the potential difference between its i/p terminals.

Op-Amps had their roots in analog computers, where they were used to accomplish mathematical operations in several, linear, non-linear & frequency-dependent circuits. The popularity of this IC as a basic building block in analog circuits is due to its flexibility. Due to its characteristics, features these are determined by an exterior component and also have a slight dependence on temperature coefficients otherwise manufacturing differences in the IC itself.

Nowadays, operational amplifiers are the most commonly used integrated circuits. The applications of these ICs include an immense array of industrial, scientific, and consumer devices. The cost of the several typical op-amps is low in reasonable production volume; but some hybrid, integrated op-amps with different performance conditions may cost over 100 dollars. Operational amplifiers may be packed as apparatuses, or used as fundamentals of more compound integrated circuits.

The operational amplifier is one kind of differential amplifier. Various kinds of differential amplifiers include the instrumentation amplifier, the isolation amplifier, the negative feedback amplifier, and the fully differential amplifier. The IC 741 looks like a ‘small chip’. But, it is general-purpose. You need to know basic information about this.

The IC 741 operational amplifier looks like a small chip. The representation of 741 IC op-amp is given below which comprises eight pins. The most significant pins are 2,3 and 6, where pins 2 and 3 denote inverting & non-inverting terminals, and pin 6 denotes output voltage. The triangular form in the IC signifies an op-amp integrated circuit.

The current version of the chip is denoted by the famous IC 741 op amp. The main function of this IC 741 is to do mathematical operations in various circuits. IC 741 op-amp is made from various stages of the transistor which commonly have three stages like differential i/p, a push-pull o/p, and an intermediate gain stage.

This operational amplifier can offer a high range of voltage gain and this can be made to function at various voltage levels and this functionality allows the device to implement in various integrators, summating type of amplifiers, and others. Even it holds the characteristics of protecting the device at the time of short circuit and has internal frequency compensating circuit networks. This IC can be manufactured in three forms and those are in 8 pin SOIC package, 8 pins Dual-in-line package, and in TO5-8 metal can form.

The IC 741 operational amplifier is used in two methods such as an inverting (-) and a non-inverting (+).

The differential op-amps comprises of a set of FETs or BJTs. The basic representation of this operational amplifier is as below:

Pin Diagram

The pin configuration of the IC 741 operational amplifier is shown below. The op amp 741 pin diagram and the functionality of each pin are explained clearly in the below section.

Power Supply Pins: Pin 4 and 7

Pin 4 and pin 7 are the negative and positive voltage power supply terminals. The power which is required for the IC to function is received from both these pins. The voltage level between these pins can be in the range of 5 – 18V.

Output Pin: Pin 6

The output which is delivered from the IC 741 op amp is received from this pin. The output voltage that is received at this pin is based on the feedback approach that is used and the voltage level at the input pins.

When the voltage value at pin 6 is high, this corresponds that output voltage is similar to the +ve supply voltage. In the same way, when the voltage value at pin 6 is low, this corresponds that output voltage is similar to the -ve supply voltage.

Input Pins: Pin 2 and Pin 3

These are the input pins for the operational amplifier. Pin 3 is considered as the inverting input while pin 3 is considered as the non-inverting input pin. When the voltage value at pin 2 >> pin 3 which means that inverting input has a high value of voltage, then the output signal is low.

In the same way, when the voltage value at pin 3 >> pin 2 which means that non- inverting input has a high value of voltage, then the output signal is high.

Offset Null Pins: Pin 1 and Pin 5

As before discussed, this operational amplifier has an increased level of voltage gain. Because of this, even minimal variations in the voltages at both non-inverting and inverting inputs those are happened because of the abnormalities in the constructional procedure or other anomaly’s will show an impact on the output.

In order to overcome this, an offset value of the voltage to be applied at pin 1 and pin 5, and this generally accomplished by a potentiometer.

Not Connected Pin: Pin 8

It is just a pin that is used to fill up the empty pin in the IC 741 Op Amp. It has no connection with any of the internal or external circuits.

Working of IC 741 Op-Amp

This section clearly explains the concept of the internal schematic and working of IC 741. A typical IC 741 is constructed with a circuit that is included with 11 resistors and 20 transistors. All these transistors and resistors are assimilated and connected as a single monolithic chip. With the below-portrayed image, the component’s internal connections can be easily understood.

Here, for the transistors, Q1 and Q2, the inverting and non-inverting inputs are connected correspondingly. Both the Q1 and Q2 transistors function as NPN emitters where these outputs are connected to a couple of Q3 and Q4 transistors. These Q3 and Q4 operate as common-base amplifiers. This type of configuration isolates the inputs that have a connection with Q3 and Q4 and so eliminates likely signal feedback which might take place.

The voltage fluctuations that take place at the operational amplifier inputs might show an impact on the internal circuit current flow and also impacts the effective functional range of any transistor that is in the circuit. So, to eliminate this from taking place, there has been the implementation of two current mirrors. The transistor pairs (Q8, Q9) and (Q12, Q13) are connected in a way to form mirror circuits.

As Q8 and Q12 transistors are the regulating transistors, they set the voltage level at the EB junction for their corresponding pair of the transistor. This voltage level can be accurately regulated to some decimals of millivolts and this accuracy permits only necessary current flow to the circuit.

One mirror circuit which is developed by Q8 and Q9 is fed to the input circuit whereas the other mirror circuit developed by Q12 and Q13 is fed to the output circuit. Also, the other mirror circuit which is the third one formed by Q10 and Q11 functions as an increased impedance connection between the -ve supply and input. This connection offers a reference level of voltage showing no loading effect on the input circuit.

The transistor Q6 together with 4.5K and 7.5K resistors will be developed into a voltage level shifter circuit that decreases the voltage level from the amplifier circuit at the input section by Vin before it gets passed to the next circuit. This is achieved to eliminate any kind of signal variations at the output amplifier section. Whereas Q22, Q15, and Q19 transistors are designed to function as class A amplifier and the Q14, Q20, and Q17 transistors develop as output phase of the 741 Op Amp.

In order to remove any kind of abnormalities at the input phase of the differential circuit, then Q5, Q6, and Q7 transistors are employed to form a configuration that has Offset null +ve and -ve and levels inverting and non-inverting inputs correspondingly.

Op-Amp Integrator and Differentiator

The below sections explains the experimental procedure of integrator and differentiator using IC 741 op amp theory.

To know about the op amp working as differentiator and integrator, we need a breadboard, resistors of value (10KΩ, 100KΩ, 1.5KΩ and 150Ω), RPS, an IC 741 operational amplifier, wires to connect, capacitors of value (0.01µF, 0.1µF), and an oscilloscope (CRO).

The integrator circuit using op amp is shown below. To form an integrator circuit and to know the output, the circuit connection to be done as explained in the below steps:

• At the input section, apply a symmetrical sine wave having a frequency of 1 kHz and amplitude of 2V which is peak to peak voltage.
• Connect the circuit’s input and output sections to the CRO channel 1 and channel 2. This connection allows observing the generated waveforms.
• Plot the observed waveforms on a graph along with the similar values observed on CRO.
• Then observe both the practical and theoretical values. This type of connection allows IC 741 op amp to be used as an integrator circuit.

The differentiator circuit using op amp is shown below. To form a differentiator circuit and to know the output, the circuit connection to be done as explained in the below steps:

• At the input section, apply a symmetrical triangular wave having a frequency of 1 KHz and amplitude of 2V which is peak to peak voltage.
• Connect the circuit’s input and output sections to the CRO channel 1 and channel 2. This connection allows observing the generated waveforms.
• Plot the observed waveforms on a graph along with the similar values observed on CRO.
• Then observe both the practical and theoretical values. This type of connection allows IC 741 op amp to be used as an integrator circuit.

Open Loop Configuration

The easiest approach to implement IC 741 Op Amp is to function it in the open-loop configuration. The open loop configuration of IC 741 is in inverting and non-inverting modes.

An Inverting Op-Amplifier

In an IC 741 op amp, pin2 and pin6 are the input and output pins. When the voltage is given to the pin-2 then we can get the output from the pin-6. If the polarity of the i/p pin-2 is +Ve, then the polarity which comes from the o/p pin6 is-Ve. So the o/p is always opposite to the i/p.

The inverting op-amp circuit diagram is shown above and the gain of the inverting op-amp circuit is generally calculated by using this formula A=Rf/R1

For example, if Rf is 100-kilo ohm and R1 is 10-kilo ohm then the gain would be -100/10=10 If the i/p voltage is 2.5v the o/p voltage would be 2.5×10=25

Non-Inverting Op-Amplifier

In an IC 741 operational amplifier pin3 and pin6 are input and output pins. When the voltage is given to the pin3 then we can get the output from the pin-6. If the polarity is +Ve at the input pin-3, then the polarity which comes from the o/p pin-6 is also+Ve. So the o/p is not the opposite.

The noninverting circuit diagram is shown above and the gain of this noninverting circuit is generally calculated by using this formula A=1+ (Rf/R1)

For example, if Rf is 100-kilo ohm and R1 is 25-kilo ohm then the gain would be 1+ (100/25) =1+4=5 If the i/p voltage is 1 then the o/p voltage would be 1X5=5v

IC 741 Op-Amp Circuit Diagram

The applications mainly include an adder, comparator, subtractor, voltage follower, Integrator, and differentiator. The circuit diagram of IC 741 op amp is given below. In the following circuit, IC 741 operational amplifier is used as a comparator. Even if we used it as a comparator the IC still observes the weak signals so that they can be identified more simply.

Specifications of IC 741 Op-Amp

The below specifications clearly explain the operating functionality and behavior of  IC 741:

• Power supply: For the functionality of this operational amplifier, it requires a minimum voltage of 5V and it can handle up to 18V.
• Input Impedance: It has a range of about 2 megaohms
• Output Impedance: It has a range of about 75 ohms
• Slew Rate: This is also the crucial attribute in choosing the operational amplifier for a high range of frequencies. This is defined as the maximum change in output voltage/unit of time. SR is measured in volts/µsec and represented as: SR = dVo/dtWith the calculation of slew rate, one can simply know the change in output where the operational amplifier varies in accordance with the variations in input frequency level. The SR gets varied with the variation in voltage gain and this is generally termed as unity gain. The slew rate value for the op-amp is always steady. SO, when the slope necessities of the output values are more than the slew rate, then there happens distortion. For an IC 741 operational amplifier, the slew rate is 0.5V/microsec which is minimal. Because of this, this IC is not used for increased frequency ranges like in comparators, filters, and oscillators.
• Voltage gain: The voltage gain is 2,00,000 for a minimal range of frequencies
• Input offset range: This IC 741 Op Amp has an input offset range in between 2 – 6 mV
• Output Load: The recommended range is > 2 Kilo Ohms
• Transient Response: This is the crucial aspect that is employed for choosing an operational amplifier in multiple applications. Together with the steady-state feedback, the op-amp includes the entire response of the practical circuit. The feedback section where a steady value is achieved before receiving the output value is termed as the transient response. Once it reaches this value, the steady value stays at that point and so because this is called a steady level. This steady phase is not based on time. The attributes of this transient response consist of overshoot percentage and rise time. It has an inverse relation to the unity-gain bandwidth of the operational amplifier.

For the operational amplifier to function as a voltage amplifier, then the increased input impedance and low output impedance values are recommended.

 741 Op-Amp Characteristics

The characteristics of the IC 741 operational amplifier include the following

• The Input impedance of the IC 741 op amp is above 100kilo-ohms.
• The o/p of the 741 IC op amp is below 100 ohms.
• The frequency range of amplifier signals for IC 741 op amp is from 0Hz- 1MHz.
• The offset current and offset voltage of the IC 741 op amp is low
• The voltage gain of the IC 741 is about 2,00,000.

741 Op-Amp Applications

There are many electronic circuits are built with IC 741 op amp namely Voltage follower, analog to digital converter, sample and hold circuit, the voltage to current and current to voltage converting, summing amplifier, etc. The applications of the IC 741 operational amplifier include the following.

• Variable audio frequency oscillator using IC 741 Op Amp
• IC 741 Op Amp based Adjustable Ripple RPS
• Audio mixture for Four channels using IC 741 Op Amp
• IC 741 Op Amp and LDR based automatic light operated switch
• DC volt polarity meter using IC 741 Op-Amp
• e-room thermometer using IC 741 Op Amp
• Listening of Bug using IC 741 Op-Amp
• Microphone Amplifier using IC 741 Op-Amp
• IC 741 Op-Amp Tester
• This is the based Protection of Short Circuit RPS
• Thermal Touch Switch Using IC 741 Op Amp
• Conversion of V to F using IC 741 Op Amp
• IC 741 Op Amp based Wind Sound Generation

Infographics of 741 Op Amp

This is all about the IC 741 Op Amp tutorial which includes the operational amplifier basics, pin diagram, circuit diagram, specifications, characteristics & its applications. Furthermore, any queries regarding this concept or 741 op-amp projects, please give your feedback by commenting in the comment section below. Here is a question for you. What is the architectural design of IC 741 and characteristics: gain v/s frequency?