Electronics - Lessons

MOSFET, BJT, and IGBT: Principles of Operation Transistors are among the most important components in modern electronics. They can be used to amplify electrical signals, switch currents, regulate power, and control other circuits. Although MOSFETs, BJTs, and IGBTs all perform similar basic functions, their internal structures and methods of control are quite different. The most important distinction is this: A BJT is primarily a current-controlled device. A MOSFET is primarily a voltage-controlled device. An IGBT is a voltage-controlled device that uses a bipolar conduction structure. Understanding this difference makes it much easier to decide which type of transistor is appropriate for a particular circuit. 1. The MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) A MOSFET is a field-effect ...

BJT Transistor Amplifier Configurations A bipolar junction transistor (BJT) can be connected in three basic ways in an amplifier circuit: Common Emitter (CE) Common Base (CB) Common Collector (CC) The word “common” refers to the transistor terminal that is common to both the input and output circuits, usually with respect to the AC signal. The three configurations use the same three transistor terminals—base, emitter, and collector—but produce very different electrical characteristics. 1. Common Emitter (CE) Basic Principle In the Common Emitter configuration, the emitter is common to both the input and output circuits. The input signal is applied between the base and emitter, while the output signal is taken between the collector and emitter. The emitter is normally connected to the signal reference (AC ground), either dir...

Operation in the CW RF generator mode and measurement of parameters of radio components using NanoVNA. The NanoVNA can function as a stable, fixed-frequency Radio Frequency (RF) signal generator ( CW Mode or Zero Span ). The generator's signal is output exclusively from port CH0 . Activating the Generator via the Menu Open the main menu by tapping the screen. Navigate to the STIMULUS section. Tap the CW FREQ button. Using the virtual keypad, enter the desired frequency and select the multiplier (e.g., M for MHz). The device will immediately switch to emitting a continuous carrier wave at the specified frequency, and the frequency sweep will stop. Generator Output Signal Characteristics Nominal output power: Approximately -13 dBm into a 50-ohm load. Waveform: Since the generator is based on the Si5351 synthesizer chip, ...

Cable Parameter Measurement and Time-Domain Reflectometry (TDR) With the NanoVNA, you can easily locate discontinuities in coaxial cables, measure the exact length of a feeder line, and find transmission line faults (such as open or short circuits) without the need to unroute or remove the cable. Time-Domain Reflectometry (TDR) This function is based on the Inverse Fast Fourier Transform (IFFT), which converts the measured vector parameters in the frequency domain into a time-domain line response. A signal pulse is sent into the cable, reflects off a discontinuity (the end of the cable, an open circuit, or a short circuit), and returns. The device calculates the exact distance based on the time delay of the reflected signal. Schematic representation of impulse probing of a cable line (TDR). Steps for setting up TDR on the NanoVNA screen: Perform an OSL calibratio...

Audio Frequency (AF) Amplifiers Actually, there is an overwhelming number of such circuits on the Internet. They vary in class, implementation, and parameters—ranging from simple designs to complex AF amplifiers with multi-loop negative feedback to minimize distortion. Building a "Hi-Fi" class AF amplifier for a ham radio receiver makes no sense for one simple reason: the signal source (the received airwaves) is far from a "musical" audio spectrum. On the contrary, it is a noisy, "dirty" audio spectrum because it reproduces "live" on-air signals. Received stations can experience fading and associated distortions, as well as high signal levels that cause noticeable clipping. Therefore, amplifying such signals with a "Hi-Fi" class amplifier is absurd, to say the least! All circuits in this section are my own designs, based on knowledge and information gathered from public Internet sources. ...