ECE 2212

EE 2212

PROBLEM SET 8

Numbering Typo Corrected

S. G. Burns

Due: 30 March 2016

Note 1: 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 that you may have for some of your “stuff” and is usable, that is supports 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 iPODs, smart phones, tablets, etc. also is interesting to me and appropriate for class discussion. 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 have. Hard Deadline for receipt of materials is class on Monday, 11 April Earlier is better! Be sure your name is in the submitted materials. They will be returned. I will award up to 30 points based upon relevance and class usability and you describing the item and technical information to the class. The meaner and badder the better

1. Refer to Text Figure P5.26 given below. Modify the default BJT SPICE model to generate a set of curves that are a reasonable match to the characteristics shown in Figure P5.26. Submit the BJT non-default model parameters and a copy of the characteristic curves that you obtained. Key parameters to change will be β and VAF.

2. Text 5.97

3. Draw and label the small-signal model for Figure 13.3 on Page 845.

4. Draw and label the small-signal model for Figure P13.10 on page 846. Using your small-signal model, derive an expression for the voltage gain, a_v = v_O/v_I in terms of the circuit elements and model elements. No numerical calculations! Observe the use of two dc supplies (independent ideal voltage sources)!

5. Draw and label the small-signal model for Figure P13.7 on page 846. Using your small-signal model, derive an expression for the voltage gain, a_v = v_O/v_I in terms of the circuit elements and model elements. No numerical calculations! Observe that this is a pnp BJT which makes no difference when working with the small-signal model. Compare your small-signal model with the Problem 3 small-signal model.

6. We are covering this topic today (Friday) which may continue into Monday’s class.

Simple and Widlar Current Sink and Source Calculations

(a) Compute a value for I_C2which is the current you would sink from a circuit requiring that current bias level.

(b) Design a pnp circuit based upon the npn circuit shown in Figure 1 that would operate as a current source, rather than a current sink, for the current computed in Part (a). Your design must include a well-labeled circuit diagram.

(c) Design a Widlar current source to sink the current computed in Part (a). Refer to Figure 2. You have a fair amount of design flexibility in R1 and the resultant value of R2.