x0x:voltagecontrolledoscillator
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x0x:voltagecontrolledoscillator [2007/09/30 16:23] hl-sdk |
x0x:voltagecontrolledoscillator [2007/09/30 18:26] hl-sdk |
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| ===== The Voltage Controlled Oscillator ===== | ===== The Voltage Controlled Oscillator ===== | ||
| {{template>.templates:schema|section=VCO|inputs=DigitalSequencer: Slide On/Off,Note|outputs=VoltageControlledFilter: Audio Out, MidiAndSync: CV Out}} | {{template>.templates:schema|section=VCO|inputs=DigitalSequencer: Slide On/Off,Note|outputs=VoltageControlledFilter: Audio Out, MidiAndSync: CV Out}} | ||
| - | The VCO is comprised of 5 sections. The first of which is the Digital to Analog converter, which takes the digital signals for the note generated by the MicroProcessor and converts them to a voltage. After that the voltage is sent to a buffer and the Slide Circuit. Then it is sent to Q26 which is responsible for (blah... marked as "antilog" on the Tb303 block schematic). Q24 and Q25 act as a special switch, which is based on a [[http://en.wikipedia.org/wiki/Silicon-controlled_rectifier|Silicon Controlled Rectifier]] which generates a Saw Wave. This waveform is then sent out to Q28 a 2SK30 JFET which is used as an operational amplifier. The output is sent to the switch, and also sent to Q8, where the saw wave is shaped into a square and back to the switch. From the switch, the output is sent to the VoltageControlledFilter | + | The VCO is comprised of 5 sections. The first of which is the Digital to Analog converter, which takes the digital signals for the note generated by the MicroProcessor and converts them to a voltage. After that the voltage is sent to a buffer and the Slide Circuit. Then it is sent to Q26 which is responsible for (blah... marked as "antilog" on the Tb303 block schematic). Q25 and Q27 act as a special switch, which is based on a [[http://en.wikipedia.org/wiki/Silicon-controlled_rectifier|Silicon Controlled Rectifier]] which, when coupled with an integrator, generates a Saw Wave. This waveform is then sent out to Q28 a 2SK30 JFET which is used as an operational amplifier. The output is sent to the switch, and also sent to Q8, where the saw wave is shaped into a square and back to the switch. From the switch, the output is sent to the VoltageControlledFilter |
| ==== Block Diagram ==== | ==== Block Diagram ==== | ||
| Line 20: | Line 20: | ||
| ==== Switch ==== | ==== Switch ==== | ||
| - | Transistors Q24, Q25 and Q27, along with C (... unreadable on the schematic) are responsible for generating the SawWave. The transistors Q25 and Q27 are set up in a special layout like so: | + | Transistors Q24, Q25 and Q27, along with C33 are responsible for generating the SawWave. The transistors Q25 and Q27 are set up in a special layout like so: |
| {{x0x:media:vcoswitch.png|}} | {{x0x:media:vcoswitch.png|}} | ||
| Line 62: | Line 62: | ||
| amount of the transistor current flows through the base, especially in | amount of the transistor current flows through the base, especially in | ||
| the case of Q27 where there is no base resistance nor diode. If Q27 is | the case of Q27 where there is no base resistance nor diode. If Q27 is | ||
| - | not suited for such an application, it will shure burn out. Most good | + | not suited for such an application, it will sure burn out. Most good |
| audio transistors with high Ft and high beta have shallow base junctions | audio transistors with high Ft and high beta have shallow base junctions | ||
| that are very sensitive. So the problem of Q27 burnout could be addressed | that are very sensitive. So the problem of Q27 burnout could be addressed | ||
| Line 70: | Line 70: | ||
| ==== Saw to Square Waveshaper ==== | ==== Saw to Square Waveshaper ==== | ||
| + | |||
| + | After the saw wave gets passed through the JFET and heads out to the waveform select switch, it heads into a jungle that I can only assume is a waveshaper. Here's a picture of the circuit: | ||
| + | {{x0x:waveshaper.png|}} | ||
/home/ladyada/public_html/wiki/data/pages/x0x/voltagecontrolledoscillator.txt · Last modified: 2016/01/28 18:05 (external edit)
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