Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Don't confuse cascode output impedance with output impedance of a single MOSFET in common source configuration. The quoted formula is referring to the latter, and only valid for the low frequency range, not for typical LNA frequencies.The gain of cascode is gm*(output impedance)^2. I want to increase the gain so I like to increase the output impedance.
Don't confuse cascode output impedance with output impedance of a single MOSFET in common source configuration. The quoted formula is referring to the latter, and only valid for the low frequency range, not for typical LNA frequencies.
is this ZL equal to 50 ohm? and how to find the Zout in cadence?Apart from this, the consideration is wrong because the gain is actually determined by Zout || ZL. In most LNA applications, ZL is smaller or maximal in the same range as Zout.
How to measure |Zout| in cadence?
1. Add a relatively large capacitance (like 1mF) to the output of the cascode and place a signal generator series with it (vdc from analogLib is good for it).
1. Where do you want to use 50Ohm? In |Zout| simulation? Not recommended. I don't understand this question actually.
2. When you measure |Zout| of your circuit you actually measue |Zout + Xc|, where Xc is the added capacitor's reactance. To keep this Xc part low, especially at low frequencies, you have to use large capacitor because Xc = 1/(2*pi*f*C).