EE 2212

EXPERIMENT 4

15 October 2015

DIODE ODDSAND ENDS CIRCUIT APPLICATIONS

20 Point Rubric

Report Due: 22 October

Note: This is a relatively short lab which shouldn’t take more than an hour or so. Since I have a visitor from GeaCom, I will have to leave about 11. Karin Larson will stop by at noon if you are still working on the lab and need some additional guidance. I would like everyone to be able to attend the noon GeaCom seminar. No time conflicts with the afternoon lab although I may be a few minutes late.

PURPOSE

Experimentally study the following circuits

Ø Double-diode clipper; both time domain and transfer (vo versus vs) characteristics

Ø AND Gate

Ø OR Gate

BACKGROUND

In addition to rectification related to power supply applications as demonstrated in Experiment 3, diode circuits are used to obtain a variety of important signal processing functions. Among them is the clipper and diode logic You will have an opportunity to demonstrate these applications both experimentally and using SPICE simulations.

Ø For example, inherent in many ICs is the use of diodes to limit input voltage transients to levels that do not damage the IC. We will observe this necessary diode protection function when we study MOS and CMOS IC technology starting next week. Virtually all MOS ICs have this integral to their design. This is also the concept of the surge protector you have for your delicate electronic stuff.

Ø Diode logic is a good way to illustrate Boolean functions using simple hardware realizations and useful for power switching applications. Refer class notes on the AND and OR gates implemented with diodes. To a degree, diode logic is often the basis underlying complex digital IC families.

COMPONENTS

Ø 1N4001 silicon diodes

Ø 1, 2, and 5 kW resistors (approximate values)

PROCEDURE

Ø Double-Diode Clipper

Construct the circuit shown in Figure 1. This circuit is called a Double-Diode Clipper. Initially, set v_s(t) = 5 sin (2p x 100t). A triangular wave with a 5 volt peak amplitude will also work. Slowly adjust the amplitude of v_s(t) and observe and record the effect on v_o(t) for various positive and negative values of V1 and V2. Also look at the transfer characteristics. You will need to switch the polarity and magnitudes of V1 and V2 (4 permutations of polarity) to note the clipping effects under all voltage polarity and amplitude conditions. To a large extent, your data collection will be qualitative. Transfer characteristics, that is v_o(t) versus v_s(t), is an excellent way to display your results. This circuit concept is integral to most MOSFET ICs to protect against ESD (Electrostatic Damage). We will talk more about ESD next week.

Figure 1 Double-Diode Clipper

Ø Diode Logic Gates

Construct the circuits shown in Figures 2 and 3 , an AND gate and OR gate respectively. Set various combinations of VA and VB voltage levels to verify the appropriate logic gate operation. Use a square wave on one of the inputs recognizing that you will need to DC offset the square wave voltage such that the minimum voltage is 0. The other input can be a zero volt or 5 volt input from your power supply. Suggest using an R pull-up and pull-down resistor on the order of 5 kW. Define the voltage ranges for the LOGIC ZERO and ONE logic levels. Refer to DiodeGates.docx on the class WEB page.

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Figure 2 Diode Logic AND Gate

Figure 3 Diode Logic OR Gate

TO THINK ABOUT AND INCORPORATE IN YOUR REPORT

Ø Did the circuits operate as expected? Justify analytically and using SPICE.

Ø How did the diode offset voltage effect the results?

Ø Suggest system applications for all the circuits.

When you go home for Fall Break, Thanksgiving, and Winter Recess, you should be prepared to do the following: (Also for Smart Phones, etc,)

I just received notification about Spring class registration that is coming up soon. Some of you may choose to work on an Energy Engineering Minor.