The History of 555 Timer IC – Story of Invention by Hans Camenzind

The 555 Timer IC is one of the renowned ICs, in the electronic circles. However, its history of invention is not known to many. This article takes you on a journey of 555 timer IC from the time of its creation to the present day time. What is a 555 timer IC? A 555 timer IC, is a multipurpose integrated circuit chip, that finds its application in timer, oscillation and pulse generation circuits. It is one of the prominent and popular inventions of the electronic world. A monolithic timing circuit, the 555 timer, is equally reliable and cheap like op-amps working in the same areas. It is capable of producing stabilized square waveforms of 50% to 100% duty ratio. The Birth of 555 Timer IC Hans R. Camenzind, designed the first 555 timer IC in 1971, under an American company Signetics Corporation. It is this design work of his, that is most prominent in Hans’s distinguished career in the field of Integrated Circuit technology. In the summer of 1971,  first design was reviewed, that used a constant current source and had 9 pins. After the review was passed, Hans thought of a new idea of replacing the constant current source by a direct resistance. This reduced the number of pins from 9 to 8, and enabled the chip to be fit in an 8 pin package instead of a 14 pin package. This new design was passed in the review in October 1971. The IC consists of 25 transistors, 2 diodes and 15 resistors. In order to define the timings, provision to attach R and C externally is provided.     In 1972, Signetics Corp. then released its first 555 timer IC in 8 pin DIP and 8 pin TO5 metal can packages, as SE/NE555 timer and was the only commercially available timer IC at that time. Its low cost and versatility, made it an instant hit in the market. It was later on manufactured by 12 other companies and became the best selling product. Although, there is a belief that this IC got its name from the three 5k resistors in its internal circuit, Hans R Camenzind revealed in his book, “Designing Analogue Chips”,  that it was Signetics manager, ArtFury’s, love for the number “555”, that led to the naming of the circuit. The basic working tutorial of timer 555 IC has been discussed in our article “555timer- A complete guide”.   Applications of 555 Timer IC: Through the years, electronic hobbyists and engineers have explored various areas where this IC can be used. From temperature  measurement to voltage regulators to various multivibrators, this IC  has found its prominent place in thousands of applications.  The implementation of 555 TIMER IC depends on its operating mode. It is this versatility of 555Timer IC, that makes it useful for many applications. Basically, a 555 timer IC has three operating modes. Bistable mode: The Schmitt trigger Monostable mode: One shot mode Astable mode: Free running mode 555 timer as a multivibrator: Depending on which type of multivibrator, (astable/monostable or bistable multivibrator) is to be used, the operating mode of 555 timer is selected. For example, if we want to design a monostable multivibrator, we will wire the 555 timer in the monostable mode. These multivibrators are used in various two state devices such as relaxation oscillators, timers and flip flops. 555 timer IC as a PWM generator: Using the variable “control” input , a 555 timer IC can be used to create a pulse width modulation (PWM) generator. The duty cycle here, depends on the analogue input voltage. This operation of 555...
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