Diodes and Rectifiers
BME253L - Fall 2025
Overview
Diodes: Basic operation and characteristics
Types of diodes: Zener, Schottky, LED, etc.
Rectifiers: Half-wave and full-wave
Diode Basics
A diode is a semiconductor device that allows current to flow in one direction only.
Forward Region: Positive voltage on the anode allows current flow; exponentially increases with voltage.
Reverse Region: Positive voltage on the cathode blocks current flow; very small leakage current.
Breakdown Region: Sudden increase in current at high reverse voltage (Zener breakdown).
Types of Diodes
Zener Diode: Used for voltage regulation; operates in reverse breakdown region.
Schottky Diode: Known for low forward voltage drop and fast switching speeds.
LED (Light Emitting Diode): Emits light when forward biased; used in displays and indicators.
Photodiode: Generates current when exposed to light; used in solar cells and light sensors.
Modeling Diodes as Switches
Rectifiers
Half-Wave Rectifier
Half-Wave Rectifier: Allows only one half of the AC waveform to pass; simple but inefficient.
How Much Power in Half-Wave Rectified Signal?
\[ V_{DC} = \frac{V_{peak}}{\pi} \quad , \quad P_{DC} = \frac{V_{DC}^2}{R} = \frac{V_{peak}^2}{\pi^2 R} \]
Full-Wave Rectifier
- Full-Wave Rectifier: Utilizes both halves of the AC waveform; more efficient and provides smoother output.
Applications of Diodes
- Voltage regulation (Zener diodes)
- Signal demodulation
- Power conversion (rectifiers)
- Light emission (LEDs)
- Photodetection (photodiodes)
Light Emitting Diodes (LEDs)
Voltage Regulation with Zener Diodes
In-class demo…
Transformers
https://www.electronics-tutorials.ws/transformer/transformer-basics.html
Clipping and Clamping Circuits
Clipping Circuits: https://www.electronics-tutorials.ws/diode/diode-clipping-circuits.html
Clamping Circuits: https://www.tutorialspoint.com/electronic_circuits/electronic_clamper_circuits.htm