In this episode, Shahriar and Shayan discuss the design and characterization of a deceptively simple CMOS inverter-based transimpedance amplifier. The the large and small signal behavior of the CMOS inverter is discussed and measured using the Keithley 2450 and 2460 source meters. The transient response is also measured using a Keysight MSO-S series oscilloscope.
The small signal gain of the circuit is calculated from small signal parameters which are extracted directly by measuring the devices I/V characteristics. The NMOS/PMOS devices used are from an ADL1105 quad-discrete transistor IC. Through the use of a shunt-shunt feedback, the CMOS amplifiers is converted to a transimpedance amplifier which is capable of amplifying the current from a photo-detector diode by a gain of 30kV/A. The feedback theory is used to calculate the gain of the amplifier. The slides for this tutorial can be downloaded here.
In this episode Shahriar explores the functionality of the popular ESP8266 SoC chip. This IC incorporates a full ISM radio as well as the physical/MAC layer for 802.11b/g/n network communication. Furthermore it includes a uC core for code execution making it a low-cost candidate for Internet of Thing applications. This video uses a Sparkfun Thing evaluation board which also includes a LiPo batter charger, voltage regular, flash memory and all the I/O pins which are accessible to the user. The block diagram of the ESP8266 is reviewed as well as the schematic of the complete Sparkfun Thing board.
By using an Arduino library and the Blynk iOS application, a cell phone and the ESP8266 can simultaneously communicate with a server running the Blynk application and transfer data between the application and the module. In this demo various components such as NeoPixel (WS2812), OneWire temperature sensor and battery monitoring functionality are implemented. The code is available here.
In this episode Shahriar and Timo demonstrate the design methodology of an FPGA based 32×32 RGB LED matrix driver. Timo has kindly devoted some of his time to describe the block diagram and the thought process which goes into designing this type of FPGA display driver. The various components of the overall system (PLL, UART, and Display Controller) are shown along with the simulation data. The outputs of the Spartan-6 FPGA board are then measured using a Keysight S-Series oscilloscope. The design of the RGB matrix is also demonstrated using a custom clock interface sent wirelessly to the unit via Bluetooth. All the FPGA design files can be downloaded here.
In this episode Shahriar builds a magical charger circuit that has an efficiency of tens-of-thousands of percent! But not to worry, it is a trick and the trick is revealed in the video. The purpose of the video is to discuss the nature of the scientific method and our society’s need for free education.
In this episode Shahriar repairs an Agilent EPM-441A (E4418A) Power Meter. The unit does not boot and displays “Loading firmware…”. After monitoring internal digital signals, the problem is traced to a faulty SRAM IC. After replacement, the unit completes the boot-up process.
Additionally, the principle operation of power sensors is reviewed including both thermocouple based, as well as diode rectifier based. The block diagram of a USB-based power sensor is examined along with a full teardown of a non-functional power sensor. The detector diode circuitry is examine under a microscope. Finally, the repaired unit is verified for calibration.
The Signal Path (TSP) is an electrical engineering video blog for industry professionals, students and hobbyists. TSP is a non-for-profit website dedicated to provide free education spanning a wide range of electrical engineering topics. Equipment reviews, tutorials and repair videos are posted regularly.