====== Simulating a common-source amplifier ======



===== Schematic entry =====

===== DC analysis =====

determinare punto di lavoro, DC operating point etc.


Vericare con una analisi parametrica in w come cambia

Plottare anche il **gain** definito con dVout/dVin,

<code>
deriv(...)
</code>

===== Transient analysis =====

**ADE L => Analyses => Choose**

Per maggiori informazioni 

<code>
spectre --help tran
</code>


Definire il gain:

**ADE L => Outputs => Setup** (or rigth click in the **Outputs** tab in the ADE L window and choose **Edit**)

<code>
0.5*( ymax(VT("/Vout")) - ymin(VT("/Vout")) )/amplitude
</code>

<code>
peakToPeak(VT("/Vout"))/peakToPeak(VT("/Vin"))
</code>



===== Frequency analysis =====

**ADE L => Analyses => Choose**

Servono voltage sources with ac specifications (AC, PC)

Per maggiori info:

<code>
spectre --help ac
</code>

Per il guadagno posso costruire a mano io l'esperessione:

<code>
abs(VF("/out")/VF("/in"))
</code>

oppure in dB = **20Log**

<code>
dB20(VF("/out")/VF("/in") )
</code>


that is equivalent to

<code>
dB20(VF("/out")) - dB20(VF("/in"))
</code>

mentre la fase e'


<code>
phase( VF("/out")/VF("/in")) )
</code>


Mettendo **AC=1** non serve neanche fare il rapporto e basta usare 

<code>
dB20(VF("/out"))
phase(VF("/out"))
</code>



Nota: **dB20** is used for **voltage gains**, whereas **dB10** is used for **power gains**


Tutto si ottiene in automatico anche come


**ADE L => Results => Direct Plot => AC Magnitude**

**ADE L => Results => Direct Plot => AC dB10**

**ADE L => Results => Direct Plot => AC dB20** 

**ADE L => Results => Direct Plot => AC Phase** 

**ADE L => Results => Direct Plot => AC Magnitude & Phase** 

**ADE L => Results => Direct Plot => AC Gain & Phase** 


calcolare il phase margin con il Calculator tramite le built-in functions **bandwith( )**
and **phaseMargin( )**


<code>
bandwidth(VF("/out") 3 "low")
</code>


<code>
phaseMargin(VF("/out"))
</code>

<code>
gainMargin(VF("/out"))
</code>



Esiste anche a built-in function for the **Gain-Bandwith product (GBW)** computation 

<code>
gainBwProd(VF("/out"))
</code>


===== Output impedance measurement =====


Attaccare in **idc** al nodo di uscita, mettere AC=1 e fare un'analisi in frequenza, a questo punto Vout in Volt e' proprio
la resistenza in Ohm (essendo AC=1 A)


To measure output impedance, regardless closed loop or open loop, u just put ideal current source Idc with ac=1 at the output, then measure the voltage at the output across frequency by running AC analysis. The voltage output is the output impedance 

 R=V/I where for I, ac=1, so V is output impedance.

 if u driving capacitive load, jsut put Idc for current source =0

 if u driving resistive load, then put Idc equal to the current output of the circuit source.





===== Noise analysis =====

**ADE L => Analyses => Choose**

Select **noise**

**ADE L => Results => Print => Noise Summary**


Se voglio the **total noise** you have integrate the spectrum

<code>
integ(....)
</code> 


Another on-line tutorial can be found [[ http://eda.engineering.wustl.edu/wiki/index.php/How_to_Perform_a_Noise_Simulation_in_Cadence | here ]]



<code>
rmsNoise(......)
</code>


Importante definire poi **ENC**

<code>
rmsNoise(......)/peakToPeak(.....)
</code>


===== Power consumption measurements =====

Da forum leggo che si usa Vdd x il valor medio della corrente che fluisce dal generatore vdd!

do a transient simulation and then the average of the current from your voltage source and multiply by //V<sub>DD</sub>//




see also [[ http://www.seas.gwu.edu/~vlsi/ece218/SPRING/reference/lab6_power_dissipation.pdf | here ]]
and [[ http://www.egr.msu.edu/classes/ece410/mason/files/guide-power.pdf | here ]]

<code>
average( IT("/V0/PLUS") )
</code>

oppure con il valore rms ??

<code>
rms( IT("/V0/PLUS") )
</code>


===== Create a symbol for the amplifier =====

**Schematic L => Create => Cellview => From Cellview...**


----

Last update: [[pacher@NOSPAMto.infn.it | Luca Pacher ]] - 27 Sep 2012