solderic.com Common emitter amplifiers provide high voltage gain and moderate current gain, making them ideal for signal amplification, while common collector circuits offer high current gain with unity voltage gain, often used for impedance matching and buffering. Explore the rest of this article to understand how each configuration can optimize Your electronic designs.
Comparison Table
| Parameter | Common Emitter (CE) | Common Collector (CC) |
|---|---|---|
| Configuration | Emitter terminal is common to input and output | Collector terminal is common to input and output |
| Voltage Gain | High (typically 50-200) | Approximately 1 (unity gain) |
| Current Gain | Moderate to high | High (close to b + 1) |
| Input Impedance | Medium (1kO to 10kO) | High (10kO to 100kO) |
| Output Impedance | High (several kO) | Low (tens of ohms) |
| Phase Relationship | Output signal is 180deg out of phase with input | Output signal is in phase with input |
| Common Applications | Voltage amplification in audio, RF amplifiers | Impedance matching, buffer stages |
| Signal Output | Voltage and power gain | Current gain, voltage follower |
Overview of Common Emitter and Common Collector Configurations
The common emitter configuration features a transistor with the emitter terminal as the common reference point, widely used for voltage amplification due to its high gain and moderate input/output impedance. The common collector configuration, also known as an emitter follower, connects the collector terminal as common, offering high input impedance, low output impedance, and unity voltage gain, making it ideal for impedance matching. Both configurations play crucial roles in analog circuit design, with the common emitter emphasizing voltage gain and the common collector emphasizing current gain and buffering.
Basic Circuit Diagrams and Operation Principles
A common emitter (CE) configuration features the emitter terminal as the common connection point, with input signals applied to the base and output taken from the collector, enabling significant voltage gain and phase inversion. In contrast, a common collector (CC) setup, also known as an emitter follower, uses the collector as the common terminal, accepts input at the base, and outputs from the emitter, providing high current gain with no voltage gain but a unity voltage output. Basic CE circuits include a biasing resistor network and load resistor in the collector path, while CC circuits typically have the load connected to the emitter, emphasizing impedance matching and buffer operation.
Voltage Gain Comparison
The common emitter (CE) configuration typically provides high voltage gain, often ranging from 20 to 200, making it ideal for amplification purposes. In contrast, the common collector (CC) configuration, also known as an emitter follower, has a voltage gain close to unity (approximately 0.9 to 1) since it primarily serves as a buffer with high current gain but low voltage gain. Understanding this voltage gain difference helps you choose the right transistor configuration for your specific circuit needs.
Current Gain Differences
Common emitter configuration offers high current gain, typically ranging from 100 to 300, making it ideal for amplification purposes. In contrast, the common collector configuration provides current gain slightly less than the common emitter but close to unity voltage gain, mainly used for impedance matching. Understanding these differences helps you select the right transistor setup based on your desired current amplification and voltage stability requirements.
Input and Output Impedance Characteristics
Common emitter amplifiers exhibit moderate input impedance and high output impedance, making them suitable for voltage amplification where signal gain is essential. Common collector configurations, also known as emitter followers, provide high input impedance and low output impedance, ideal for impedance matching and buffering applications. The high input impedance of common collector stages ensures minimal loading on the preceding circuit, while their low output impedance enables driving low-resistance loads effectively.
Phase Relationship and Signal Inversion
The common emitter configuration provides a 180-degree phase shift between the input and output signals, resulting in signal inversion, whereas the common collector configuration offers a phase relationship with no inversion, maintaining the input signal's phase. Common emitter amplifiers are favored for voltage gain due to this inversion property, while common collector amplifiers, known as emitter followers, are primarily used for impedance matching and buffering without phase change. Understanding these phase relationships is crucial for designing amplification circuits tailored for specific signal processing needs.
Applications of Common Emitter Configuration
Common emitter configuration is widely used in amplifier circuits due to its high voltage gain and moderate current gain, making it ideal for signal amplification in audio and radio frequency applications. This configuration is also prevalent in switching circuits because it provides significant phase inversion and efficient control of the transistor's output. Your electronic projects benefit from common emitter stages when precise voltage amplification and signal processing are required.
Applications of Common Collector (Emitter Follower)
The common collector, or emitter follower, finds widespread application as a voltage buffer due to its high input impedance and low output impedance, effectively matching impedance between high-impedance sources and low-impedance loads. It is extensively used in impedance matching circuits, preamplifier stages, and voltage regulators to provide current gain without voltage gain. Its ability to maintain signal integrity while isolating stages makes it essential in audio amplifiers and sensor interface circuits.
Advantages and Limitations of Each Configuration
The common emitter configuration offers high voltage gain and moderate current gain, making it ideal for amplification purposes, but suffers from phase inversion and relatively lower input impedance. The common collector configuration provides high current gain and very high input impedance with output voltage nearly equal to the input voltage, making it excellent for impedance matching, yet it offers no voltage gain. Each configuration's choice depends on the desired balance between voltage amplification, current amplification, and impedance characteristics in circuit design.
Selection Criteria for Amplifier Design
Common emitter amplifiers offer high voltage gain and moderate input impedance, making them ideal for voltage amplification in signal processing applications. Common collector configurations provide high input impedance and unity voltage gain, best suited for impedance matching and current buffering. Your choice depends on whether voltage gain or impedance matching is the primary design requirement.
common emitter vs common collector Infographic
