490 Analog Voltage Controlled Oscillator

490 : Analog Voltage Controlled Oscillator

Design render
  • Author: Georg Boecherer
  • Description: A voltage controlled oscillator with 4 differential stages.
  • GitHub repository
  • Clock: 0 Hz

How it works

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.

How to test

Connect a control voltage or current to the analog input pin ua[0] and observe the oscillating signals at the digital output pins.

External hardware

DC power supply for the control voltage/current, oscilloscope for monitoring the outputs.

IO

#InputOutputBidirectional
0tap 0 signal
1tap 1 signal
2tap 2 signal
3tap 3 signal
4tap 4 signal
5tap 5 signal
6tap 6 signal
7tap 7 signal

Analog pins

uaanalogDescription
03bias control signal
12optional bias control signal

Chip location

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