741 0p Amp

Introduction to Operational Amplifier(op-amp)

Much reduced and reliability increased.Probably the best-known op.amp is the type 741. This op.amp makes an ideal experimental device since it is electrically robust and can be freely handled without a wide range of voltages, and is “frequency compensated”. This ensures that it cannot oscillate unpredictably and uncontrollably – a problem often associated with highgain amplifiers. This op.amp is housed in an 8-pin d.i.l. package. The package and its pinout symbol are shown in Photo  and Fig.1 respectively. So how does it work? A clearer view of the op.amp symbol associated with the 741 (and many other types of op.amp) is shown in Fig.2. Note that the power supply connections are via pin 7 (positive) and pin 4 (negative). The output is from pin 6. There are two input pins, labelled – and +. The minus symbol indicates the “inverting input” and the plus symbol indicates the “non-inverting input”. The job of the op.amp is to amplify the difference in voltage between these two inputs, and apply the result to the output. This may sound complicated, but in practice one or other input is generally connected to a fixed voltage and the signal you wish to amplify is applied to the other input.There are three unused pins, shown in Fig.1, but not in Fig.2. Two of them (pins 1 and 5) are for special functions such as “fine-tuning” when the op.amp is required to amplify d.c. signals. You will rarely, if ever, need these two pins and they should remain unconnected in your circuits. Pin 8 has no function. It is worth noting, though, that other single op.amp types may have different functions for pins 1, 5 and 8. Before continuing, we need to examine the type of power supply (PSU) often used with op.amps – a dual-rail power supply.This can be understood if you see how it is created from batteries. We will assume two 9V batteries are employed as shown in Fig.3.The two batteries are connected in series, and the point at which they join is called 0V. Note that calling this point 0V is for mathematical convenience – it is not necessarily connected to “ground” or “earth”. We can now refer to the positive side as +9V and the negative side as –9V. Mains driven dual-rail supplies are also available. Connecting an op.amp to a dual-rail supply allows it, in many instances, to amplify a.c. signals (e.g. audio signals) without using bulky and expensive d.c. blocking capacitors.

Op Amp applications handbook

Op Amps, design, applications, and troubleshooting

Basic Electronics Devices Circuits And It Fundamentals

Electronic Measuring Instruments

Electronics Engineering