The IIS Chip Gallery
Virtual_Analog_Synthesizer (2006)
by
| Application | Audio |
| Technology | 250 |
| Manufacturer | UMC |
| Type | Semester Thesis |
| Package | LCC84 |
| Dimensions | 2500μm x 2500μm |
| Voltage | 2.5 V |
| Clock | 25 MHz |
In this student IC design project, a digital ASIC has been developed which imitates famous analog music synthesizers as Moog or Sequential Prophet-10. These machines consist of a multitude of analog components that can be interconnected to realize an almost infinite variety of different systems. The components are voltage-controlled oscillators (VCO), voltage-controlled filters (VCF), and voltage-controlled amplifiers (VCA). The VCOs are controlled to generate the frequency of the note including strong harmonics. Therefore, pulse trains, triangular or saw-tooth waves are available. The VCFs then form the harmonic spectral behavior while VCAs in conjunction with envelope generators start and stop the tone comparable to musical instruments.
Translating such a system into the digital domain is not as simple as might be expected. Disregarding the required band limitation for time-discrete systems leads to aliasing and to the typical sound of cheap digital equipment. The students put a lot of good ideas and effort into the design in order to avoid this. The mentioned components can be interconnected through a microprocessor-controllable connection matrix. A music synthesizer can now be constructed by applying one ASIC per voice. The fabricated chip has been found to be fully functional during the testing by the students.