EEL6935: HW#2

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EEL 6935: HW#2

Due Friday, September 27, 2002 in class. Late homework loses $e^{\char93  of days late} -1$ percentage points. See the current late penalty at
http://www.cnel.ufl.edu/hybrid/harris/latepoints.html

1.

Solve for $I_{out}$ as a function of $I_1$ and $I_2$. As usual, first, assume $\kappa=1$ and derive your answer. Then assume $\kappa$ is the same for all transistors but not equal to one and derive your answer. Show all of your work and explicitly state all assumptions, e.g. which transistors are in saturation, subthreshold operation, matching of devices, etc. You will have to think a little bit more about this circuit than those in HW#1.

2.

Derive another expression for the output voltage limitation of the five-transistor transconductance amplifier using the following constraint. Assume that the value of $V_{out}$ is valid until it changes the output current by $I_B$ from its nominal value. Give a simplified rule of thumb for the limits of $V_{out}$ and, as usual, state all of your assumptions.

For the final questions, you must have access to a circuit simulator. Examples include CADENCE SPECTRE, PSPICE, HSPICE, and winspice but use whichever simulator you feel comfortable with. Note that winspice is shareware that is available from www.winspice.com. We will be using the 0.6um AMI process available through MOSIS. Complete information about the process is available through
http://www.mosis.org/Technical/Processes/proc-ami-c5n.html
UF CADENCE users will already have this process available but other simulators may require the following model files available at
http://www.cnel.ufl.edu/hybrid/courses/EEL6935/nmos.txt
and
http://www.cnel.ufl.edu/hybrid/courses/EEL6935/pmos.txt

3.

For a 6um x 6um nfet transistor, plot the Ids vs. Vgs curve for the device. Calculate the approximate value of $\kappa$. Completely describe how you performed the calculation. Also, come up with a rule for defining what the threshold of the transistor is.

4.

For a 6um x 6um nfet transistor, plot the Ids vs. Vds curve for the device. Calculate the approximate value of the Early Voltage $V_E$. Completely describe how you performed the calculation. Also, come up with a rule for defining what the saturation voltage is.

5.

Verify your solution of Problem 1 for $I_{out}$ as a function of $I_1$ and $I_2$. Show plots and compare your theoretical solution to the simulation.

6.

Verify the output voltage limitation of the transamp that you discussed in Problem 2. How accurate are your limits on $V_{out}$ for a variety of $V_1$ and $V_2$ values?