Engineer4ever
Member level 3
Hi,
I am designing an 5-stage oscillator using Maneatis cells. Now, I do have a hard time knowing what things to do first. I designed the Maneatis delay cell but in order to keep the PMOS loads in triode region, I had to fix the value of (bp), which is actually (Vctrl) of the VCO, so that the loads operate in triode region. The problem is, the range of (bp) that keeps the PMOS loads in triode is quite small, like 50mV range. If I increase the value of (bp), the PMOS loads start operating in the saturation region. I don't know how can I size the transistors of the cell so that it works on a wider tuning range and still keep the transistors operating in the right regions. The design steps confuse me: should I design the delay cell alone at the beginning, or should I place the 5 stages together as a VCO and then start sizing the transistors? I am having a hard time figuring out the steps to be followed, especially that I have never designed a VCO before.
Thanks,
I am designing an 5-stage oscillator using Maneatis cells. Now, I do have a hard time knowing what things to do first. I designed the Maneatis delay cell but in order to keep the PMOS loads in triode region, I had to fix the value of (bp), which is actually (Vctrl) of the VCO, so that the loads operate in triode region. The problem is, the range of (bp) that keeps the PMOS loads in triode is quite small, like 50mV range. If I increase the value of (bp), the PMOS loads start operating in the saturation region. I don't know how can I size the transistors of the cell so that it works on a wider tuning range and still keep the transistors operating in the right regions. The design steps confuse me: should I design the delay cell alone at the beginning, or should I place the 5 stages together as a VCO and then start sizing the transistors? I am having a hard time figuring out the steps to be followed, especially that I have never designed a VCO before.
Thanks,