Problem 1: You have decided to build a small computer from discrete transistors as a demonstration. After researching the available technologies, you have decided to base your design on NMOS logic, using a 3-input NOR gate as your basic building block, … Continue reading

__# Category Archives: Test Your EQ (Engineering Quotient)

Problem 1: The diagram below is a simplified illustration of a switchmode “buck” DC-DC converter with synchronous (active) rectification. The switching elements are shown as MOSFETs, with the associated body diodes drawn explicitly. The details associated with driving the MOSFET gates … Continue reading

__Problem 1: What do we call a network of gates that has no feedback of any kind? What is its key characteristic? Answer 1: A network of gates that has no feedback is called “combinaotorial logic”, or sometimes “combinational logic”. Its defining characteristic … Continue reading

__Answer 1—The frequency generated at the QB output of the counter is 16.000 MHz × 3 / 13 = 3.6923 MHz. The ratio between this and 3.6864 MHz is 1.0016, so the error expressed as a percentage is +0.16%. This is well within … Continue reading

__Problem 1—Let’s get back to basics and talk about the operation of a capacitor. Suppose you have two large, flat plates that are close to each other (with respect to their diameter). If you charge them up to a given … Continue reading

__Problem 1—Let’s talk about noise! There are different types of noise that might be present in a system, and it’s important to understand how to deal with them. For example, analog sensors and other types of active devices will often … Continue reading

__Problem 1—What is an R-C snubber, and what is a typical application for one? Answer 1—An R-C snubber is the series combination of a resistor and a capacitor that is placed in parallel with a switching element that controls the … Continue reading

__Problem 1—When designing a pair of band-splitting filters (for, say, an audio crossover), why is it important to match frequencies of the –3-dB points of the low-pass and high-pass responses? Answer 1—The cutoff frequencies of the two filters should be … Continue reading

__Question 1—A divider is a logic module that takes two binary numbers and produces their numerical quotient (and optionally, the remainder). The basic structure is a series of subtractions and multiplexers, where the multiplexer uses the result of the subtraciton … Continue reading

__PROBLEM 1 Can you name all of the signals in the original 25-pin RS-232 connector? ANSWER 1 Pins 9, 10, 11, 18, and 25 are unassigned/reserved. The rest are: Pin Abbreviation Source Description 1 PG – Protective ground 2 TD … Continue reading

__PROBLEM 1 Construct an electrical circuit to find the values of Xa, Xb, and Xc in this system of equations: 21Xa – 10Xb – 10Xc = 1 –10Xa + 22Xb – 10Xc = –2 –10Xa – 10Xb + 20Xc = … Continue reading

__PROBLEM 1 What is the key difference between the following two C functions? #define VOLTS_FULL_SCALE 5.000 #define KPA_PER_VOLT 100.0 #define KPA_THRESHOLD 200.0 /* adc_reading is a value between 0 and 1 */ bool test_pressure (float adc_reading) { float voltage = … Continue reading

__Problem 1—Tom, an FPGA designer, is helping out on a system that handles standard-definition digital video at 27 MHz and stores it into an SDRAM that runs at 200 MHz. He discovered the following logic in the FPGA (see Figure … Continue reading

__Problem 1 Suppose you have an ordinary switch mode buck regulator. The input voltage is 100 V, the switch’s duty cycle is exactly 50%, and you measure the output voltage as 70 V. Is this converter operating in continuous conduction … Continue reading

__The answers to the Circuit Cellar 274 Engineering Quotient are now available. The problems and answers are listed below. Problem 1—What is wrong with the name “programmable unijunction transistor?” Answer 1—Unlike the original unijunction transistor—which really does have just a … Continue reading

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