adesign wrote on Jan 15th, 2007, 6:04am:Dear all,
I'm designing a ring-oscillator with 5 inverter stages(current starved inverters). Each inverter stage has two current sources. One is to charge the capacitor formed by the next stage and the other is to discharge that. Both the current sources have the same dc current level.(The basic schematic is attached herewith for one of the inverter stage).
For keeping both the current sources(top and bottom) in saturation, we need to limit the swing of the inverter chain. I'm trying to reduce that by reducing the length as well as reducing the current supplied by the sources. However, I've reached the limit of minimum length of the devices. I'm also seeing that whenever the output frequency is high then the swing is limited whereas when the output frequency is low the swing is very high(almost rail-to-rail).
Could you please suggest me any alternate way to reduce the swing or to keep the sources in saturation?
Best regards,
hi,
i think you can try to add a diode connection mos transistor onto the output. in this way,
the tail current can keep acting as a current source. this is an original idea, which is not suitable for your case.
but after some modification, you can realize a good clipping swing.
good luck
jeff