A voltage controlled oscillator (VCO) using 4 differential stages and a bias controller. At each stage, the outputs are low-pass filtered by nfet transistors connected as capacitors to ground.
The first analog pin ua[0]
can be used as input to control the frequency by changing the gate voltages of nfet current sources connected to ground. The second analog pin ua[1]
can be used to monitor the gate voltage generated by the bias controller of the pfet current sources connected to VDD. Alternatively, the second analog pin ua[1]
can be used as input pin to overwrite the bias controller.
The 4 differential stages provide in total 8 tap signals with phase differences of 360/8. The 8 tap signals are converted to digital signals by buffers and output at the 8 digital output pins uo[0]
to uo[7]
. NB: the 8 tap signals are ordered by wiring convenience, not by phase.
For further information, see github.com/gbsha/tt08-analog-vco for updated information.
Connect a control voltage or current to the analog input pin ua[0]
and observe the oscillating signals at the digital output pins.
DC power supply for the control voltage/current, oscilloscope for monitoring the outputs.
# | Input | Output | Bidirectional |
---|---|---|---|
0 | tap 0 signal | ||
1 | tap 1 signal | ||
2 | tap 2 signal | ||
3 | tap 3 signal | ||
4 | tap 4 signal | ||
5 | tap 5 signal | ||
6 | tap 6 signal | ||
7 | tap 7 signal |
ua | analog | Description |
---|---|---|
0 | 3 | bias control signal |
1 | 2 | optional bias control signal |