Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
With tail current source, the current consumption is limited and known, so the voltage swing is controlled as well. The PSRR is high.
Without the tail source, the phase noise would be the best.
As a compromise a tail resistor is used in many designs.
Current source will consume headroom as well!
The intention of using a resistor here is not to have huge impedance as that of a current source.
The resistor is used only not to let the current go haywire. For the high purity VCO's that you are speaking about, the currents would be high and limit the resistor to a low value. It is a compromise., if you are OK with the power consumption without the tail resistor, that would be great, but otherwise it is a simple solution.
Try to use a resistor with CTAT characteristics so that the current increases as gm decreases due to temperature increase.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
