In this episode Shahriar presents a tutorial on the design and characterization of a single-stage low-noise bipolar amplifier suitable for audio applications. Given a set of specifications, a common-emitter topology is investigated. The circuit employs a beta-insensitive biasing scheme which is simultaneously optimized for maximum output swing. The small-signal gain of the circuit is calculated and the bandwidth is set for audio frequencies. A non-inverting operational amplifier is used as a second stage to achieve the desired overall gain. The circuit is assembled on a breadboard where the gain and bandwidth are measured and compared with design specifications. As the final experiment, the circuit is used to amplify signals from a microphone. All documents can be downloaded from here.
In this episode, Shahriar investigates the theory and experimental results of the impact of extreme low temperatures on passive and active components. Liquid Nitrogen in used in a transparent glass Dewar where different components can be fully submerged in the liquid. Various types of resistors are compared for their temperature stability. An electromagnet which uses Copper coils is used to generate a magnetic field at a constant power consumption at both extreme temperatures. The impact of liquid nitrogen on the junction voltage of an NPN device is measured as well as the frequency shift of a CMOS ring oscillator. Finally, the wavelength shift of an LED submerged in liquid nitrogen is studied. There is a puzzle at the end of this video, please share your thoughts in the comments section. All documents can be downloaded from here.
In this episode Shahriar uses a few components to beyond what there were originally intended for in order to setup an optical link! By using a BlinkM RGB LED, a Color Sensor, and two PIC USB Boards from Sparkfun Electronics, a stand-alone optical link is established. Various theories of operation, including multilevel data transmission, signal constellation and detailed circuit diagrams are also presented. The final result is an 8-PAM, 3-Wavelength optical link with a colorful three-dimensional constellation graph. The code for the transmitter IC, receiver IC and Matlab functions are available to download from here.
In this episode Shahriar explores the world of filters! Starting from a simple lumped RC filter, he briefly covers the theory before moving onto measurement techniques. The bandwidth of the filter is verified experimentally in the time domain. A more complex RLC band-stop filter is also demonstrated with a tune-able inductor which is measured using an RLC meter. Using a Rigol spectrum analyzer with built in tracking generator and an active probe, the frequency response of the filter is measured. Several other packaged filters are also demonstrated and a microwave band-pass filter is disassembled to reveal its internal construction.
Moving onto “undesired filters”, a Tyco backplane board is presented and the bandwidth limitation of the backplane traces are measured. A Xilinx FPGA board equipped with a Virtex II PRO is used to generate a 1.5Gbps PRBS data stream through the Tyco board. After observing the frequency composition of the date, pre-emphasis equalization is used to compensate the backplane frequency limitations. Eye diagram measurements verify the benefit of pre-emphasis equalization to combat inter-symbol-interference (ISI).
I would like to acknowledge my friend and colleague, Dr. Timo Pfau for his expertise in setting up and configuring the Xilinx FPGA board.
In this episode Shahriar investigates the impact of linearity and distortion on analog circuits. The source of a non-linear input/output characteristic is presented in three different domains: mathematical, time domain and frequency domain. After the theoretical discussion, a sample circuit is built and tested to illustrate real time signal distortion. The criteria for measuring non-linearity is also presented. Furthermore, the importance of a two-tone test for bandwidth limited circuits is shown theoretically and experimentally. There is another quiz in this episode! Please discuss the answer on the forum or in the comment section.
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This is "The Signal Path dot com"! An electrical engineering video blog for students, hobbyists and hackers. I do equipment reviews, teardowns, circuit design tutorials, testing procedures and more! Subscribe to my RSS, join the community forum and participate in the discussions.