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https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> shunt peaking configuration https://designers-guide.org/forum/YaBB.pl?num=1176839865 Message started by golden_falcon10 on Apr 17th, 2007, 12:57pm |
Title: shunt peaking configuration Post by golden_falcon10 on Apr 17th, 2007, 12:57pm I try to design High Frequency Amplifier, I use shunt peaking configuration as shown in attachment. How …? 1-I calculate the total capacitance at the drain of M2. 2-Can I calculate it using Dc Analysis using Cadence Spectre Calculator/tools because there is many cap like (Cgd, Cdg, Cdd…) in dc operating point how I choose between it to calculate the total capacitance at the drain of M2. 3-the value of this capacitance take –ve value >>>>HOW??? |
Title: Re: shunt peaking configuration Post by Geoffrey_Coram on Apr 18th, 2007, 4:07am If you're manually adding up Cxy, you need to pay attention to the definition as Cxy = -dQx/dVy, see the minus sign. Spectre (and other simulators) support a CAPTAB option that can print the total capacitance at a node, but this will give misleading numbers if there is a small drain resistor (you have to find the capacitance on the internal drain of M2). Another method is to put a small-signal source on the drain: i2 (0 m2_D) isource dc=0 mag=1 then measure the small-signal (ac) voltage, and compute: Ceff = imag(1/vac(m2_D)) / (2 * pi * freq) where "freq" is the frequency where you measured the ac voltage. This is because I = Y V, where the admittance Y is the parallel combination of the effective conductance and capacitance: Y = Geff + j w Ceff I = 1 (mag=1 on source i2) Thus, Y = 1/V, and imag(1/V) = imag(Y) = w Ceff, so Ceff = 1/ (2 * pi * freq) * imag(1/V) |
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