There are many 741 compatible chips readily obtainable; however, the problem is that many students and colleges are not aware of the different manufacturers and the model numbers. Consequently, some chips have been getting expensive due to students relying too much on one model and manufacturer.
The 741 is the one everyone thinks of when looking for a general-purpose amplifier, however, if you rely too much on the same chip and seller, they will sometimes artificially hike up their prices. You can make your budget stretch further if you look for cheaper equivalents.
Almost all the modern 8-pin operational amplifiers take their architecture from the earlier 741 chip. Many manufacturers have made minor changes to the original design, however for the most part they are pinout equivalents, and the same formula for gain calculation applies.
If you were using an op amp for simple educational experiments to calculate the gain, or perhaps for simple basic op amp circuits, then many cheaper equivalents would perform just as effectively, and save you money. I have compiled a list of my favourite chips that are readily available and affordable.
The LM741 is a classic op amp chip and as you can see, it has a very simple and standard layout that is identical to all the chips mentioned on this page. This is a general-purpose amplifier utilising bipolar junction transistor technology.
These come in two flavours, the 741 and 741 A can operate on split voltage rails of +22 V and -22 V, whilst the LM741C requires +18 V and -18 V.
Even with all the modern day equivalents, the LM741CN is still a very cost effective chip at around 54p each or 32p when you buy 100 from Farnell.
CA3140E is pin equivalent to the LM741. There is a minor difference in that pin 8 is for the strobe function, which controls the output, however, for basic op amp circuits it is not used.
The CA3140E is a direct replacement for the 741, and the manufacturers designed it with this being the main purpose.
The input and output stages of this chip use MOSFET transistors, hence, Bi-MOS technology is utilised in its design.
TL081CN is another favourite of mine because it is affordable. You can pick one of these up from Maplin for around 62p whilst you are on your way to the chip shop.
This is a general-purpose operational amplifier with a JFET input, which is even better because its input impedance will be high. This means you could connect the inputs directly to a signal source with minimal impedance issues.
Your basic op amp circuit configurations will be the same and you will be using the same formulas.
The TL061CP is a great op amp chip manufactured by Texas Instruments. Just like the TL081CN, it has a JFET input stage; however, this IC is a low power version. You can get these from RS at very affordable prices.
TL071CP is also another great operational amplifier by Texas Instruments. This is the low noise version, which is extremely useful for high-fidelity audio applications. It has JFET inputs and is pin compatible with the 741.
ST Microelectronics used to manufacture the LF351N, and it had JFET inputs and wide bandwidth. There is some old stock on eBay, and you could get ten chips from China for approximately £2.50. However, Farnell have the LF356N, which is an equivalent for 38p.
MC33171N by ST Microelectronics is a general-purpose operational amplifier. This is one of my favourites as it is almost identical to the old 741 in technology. This one is the most affordable I could find from Farnell at just 38p each or 29p when you buy 100.
Texas Instruments TL0xx Range
|TL031||TL031CP||38p||Low Power, Low Offset, Enhanced JFET|
|TL051||TL051CP||54p||Low Offset, Enhanced JFET|
Texas Instruments have one of the largest ranges of integrated circuits that are 741 pin compatible, with JFET inputs. Here is a list showing the approximate price for one at Farnell. Obviously, it will be cheaper for bulk purchase.
MCP601 and MCP603
The MCP601 and MCP603 are by Microchip Technology Inc., and cost approximately 33p and 26p respectively. These CMOS operational amplifiers will operate on a voltage as low as 2.7 V, and accept a maximum of 6 V. These are ideal for battery powered circuits and portable devices. The common mode input voltage range will go 0.3 V below ground, making it ideal for single-supply circuits.
Both chips are pin identical to 741, except the MCP603 has a chip select on pin 8. This is useful if you wanted to switch audio signals, otherwise, you could always tie it permanently to ground.
The OPA602 is a high-speed precision operational amplifier with a dielectrically isolated FET (Difet) construction. This is the extreme end of operational amplifiers manufactured by Burr-Brown and costs approximately £8.70 per chip. If you required high-speed and precision, and money was no object, then this IC is ideal for precision instrumentation, medical equipment, and professional audio.