EE 2212

PROBLEM SET 7

S. G. Burns

Due: Friday, 26 March 2021

Revised with corrected dates for extra credit project.

EXTRA CREDIT OPPORTUNITY

Up to 30 Points added to your end-of-the-semester Quiz Point Total. How do you earn this? I want circuit diagrams and specifications for power amplifiers and related equipment that you may have for some of your “stuff” and is usable, that is, supports ZOOM in-class discussions when we get to power amplifiers towards the end of the semester. Information such as circuit diagrams, specifications for your sound systems, guitar amps, car stereos, powered sub-woofers, associated power supplies, speaker systems, etc. I define power loosely in that information on your portable electronics such as wireless earbuds, smart phones, tablets, etc. also is interesting to me and appropriate for class discussion. Homebrew projects in these categories are appropriate. I would like to borrow the material to supplement our class discussions on power amplifier circuits. Do not just go to the WEB for information that doesn’t relate directly to stuff you or your parents have. Hard Deadline for receipt of materials is to be sent to me as an e-mail attachment (PPT or PDF) by Wednesday, 14 April, 4 pm. Earlier is better so I can do a decent scheduling job.! Be sure your name is in the submitted materials. I will award up to 30 points based upon relevance and class usability and you describing the item and technical information to the class. Your 3-5 minute presentation via a ZOOM share will be scheduled for Wednesday or Friday (21 or 23 April). Feel free if to discuss what you have with me if you have questions. The meaner and badder stuff, the better.

The following problems provide practice in working with small-signal models. Use the basic voltage-controlled current generator FET small-signal model with λ (Lambda) =0. In addition to answering the text questions, you are to draw and label the resultant small-signal model circuit diagrams. Express your derivations symbolically; that is no calculations are required. These problems also will familiarize you with the text FET symbol notation variations. It is important that you label circuit nodes carefully.

1. Draw the small-signal model for Figure P13.5. After you have obtained the small-signal model, derive an equation for the voltage gain defined by av = vo/vi. Observe that no numerical calculations are required. Note that this circuit uses an NMOS. This circuit is a common-source.

2. Draw the small-signal model for Figure P13.8. After you have obtained the small-signal model, derive an equation for the voltage gain defined by av = vo/vi. Observe that no numerical calculations are required. Note that this circuit uses a PMOS. This circuit is a common-source.

3. Draw the small-signal model for Figure P13.9. After you have obtained the small-signal model, derive an equation for the voltage gain defined by av = vo/vi. Observe that no numerical calculations are required. Note that this circuit uses an NMOS. The circuit is a common-gate.

4. Small-Signal Model derivation for a cascade amplifier excerpted from an old quiz.

(a) Sketch and label a small-signal model for this circuit which consists of two Common Source amplifiers in a cascade configuration. Assume all capacitors are large at the frequency of interest . Your model should be complete and well-labeled. Assume λ= 0.

(b) Derive an expression for the voltage gain defined by Av = Vout/Vs . Observe no numerical calculations are required.

5. Synthesize a Resistor With A Switched Capacitor Circuit

Design a switched capacitor circuit that could be used to synthesize a 10 kW resistor where the high frequency band limit, of any signals passing the equivalent synthesized resistor, is in the range expected from your audio band-limited smart phone. I will accept any reasonable number for what you consider the highest frequency for speech one could expect from your smart phone .

Your design should include:

· Well-labeled circuit diagram

· Design equations with key component values and an appropriate clock frequency.

· Clock waveforms .

6. Switched Capacitor Low Pass Filter Design (excerpted from an old quiz)

Use the basic concepts from the equivalent resistor design discussed in class , design a switched capacitor LPF that replaces the analog LPF; a topology we studied extensively the first couple of weeks of the semester.

Design this circuit as a switched capacitor low-pass filter. Your design should include:

· Well-labeled circuit diagram.

· No resistors-That is replace the two resistors with two switched capacitors and four FETs. Your design should include appropriate W/L ratios for the four FETs. An appropriate clock frequency for operation at input signal frequencies to 5 kHz.

· Key clock waveforms with the correct phasing for the four FETs illustrating the operation.

It’s all Greek to me