555 tone generator circuit

Posted on Feb 5, 2014

This circuit takes the outputs from two different 555 multivibrators and combines them using a summing Op Amp. Shown only to depict another implementation of a 555 timer, most of the back ground calculations being covered under the other topics in this section. The standard configuration for a 555 Astable multivibrator is shown to the left. The ci

555 tone generator circuit
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rcuit is shown again to reference the next schematic which contains two individual astable circuits. Resistors R1 and R2 in combination with capacitor C1 select the output frequency, however the frequency is not relevant to the following discussion [adding two outputs together]. This is one topic of a number covering the 555 timer, with this page covering a combination of 555 timers and operational amplifiers. The circuit is composed of three ICs; two 555 timers and an operational amplifier. However a dual 556 timer could have been used, but a single 555 timer was used to provide the same pin out given on the other pages covering the 555. The operational amplifier, which is labeled Adder, could be almost any Op Amp including a single, dual or quad package; although only one amplifier is required. The circuit consists of two individual pulse generators, operating at different pulse widths, and connected to a three input summing amplifier. The third input shows a symbol for a pulse generator, and only depicts the fact that any number of inputs could be used The timers could be set to operate at the same pulse rate, but that couldn`t serve much purpose, as there addition wouldn`t change anything. The addition of two identical waveform produces the same output as the input, but at a different voltage level. However if the output was required to be at a different voltage level the Vcc could just be taken to a higher voltage,...

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