I am designing a LC CMOS Tail injection based Oscillator but somehow the node voltages are constantly showing errors. The circuit schematics are enter image description here

The properties of MOSFETs are as followed:

enter image description here

Node Voltages: enter image description here

I am getting weird results in which the Node Voltages are constantly shooting up to Mega-Volts range. It would be helpful if you could suggest what am I doing wrong possibly. Thanks in Advance

  • \$\begingroup\$ Off topic, but unless you turned the text anchors to be visible on purpose (the small circles), if you press A you'll toggle them back to be invisible. \$\endgroup\$ – a concerned citizen Jul 10 '20 at 19:16

You are using ideal tank, add a resistor in parallel with the LC tank, should work then.
Also, you have a floating node between the drains of the MOS. Split the inductor as a series combination of two 0.04nH inductors and connect the node in between to VDD/2 = 1.25V. Will definitely work then.

  • \$\begingroup\$ Tried using the Resistors with values ranging from 100ohms to 1M ohms in parallel to the LC tank, but didn't help. \$\endgroup\$ – Aksh Chordia Jul 10 '20 at 9:53
  • \$\begingroup\$ @AkshChordia Also try a small resistor in series with the inductor. May or may not help. \$\endgroup\$ – Russell McMahon Jul 10 '20 at 10:22
  • \$\begingroup\$ @AkshChordia See edits\ \$\endgroup\$ – sarthak Jul 10 '20 at 14:16
  • \$\begingroup\$ @sarthak Thanks! Your suggestion works. By the time I also realised that I was a bit harsh using a constant current source. I tried inserting an N-MOS always in saturation for tail current injection initially but didn't help initially. Adjusting the Initial conditions and changing the LC values makes the circuit work. \$\endgroup\$ – Aksh Chordia Jul 10 '20 at 15:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.