Transistor Amplifier Calculator

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Transistor Amplifier Calculator

This web-based calculator helps you design single-stage transistor amplifiers / buffers using either the common emitter or common collector configuration.

It automatically computes key resistor and capacitor values based on your inputs, suggests nearest standard components, and estimates frequency response, gain, and signal swing limits.

The goal is to provide a quick and educational way to prototype audio-frequency amplifier circuits with realistic transistor behavior.

Use the visual plots and export options to support your learning, documentation, or experimentation.

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Last updated: 2025.06.09 at 16:03 CET

Amplifier Schematic

Click on the schematic for amplifying it

Amplifier Chain

Amplifier Name: Timestamp:

Import Chain Import Single Amp

Amplifier Chain Summary

Results

* Capacitor values (Cin, Cout, Cbypass) are minimum required for target cutoff frequency. Using larger values is safe and improves low-frequency response.

Graphs

Log scale X-axis (Gain plot)

Hover the graphs to see specific value pairs.

Q1 Transistor Output Characteristics

Formulas Used:

Notes / Assumptions

Common Emitter Amplifier

The common emitter amplifier gains its name from the fact that the emitter is common to both the input and output circuits. It is the most common of the formats for transistor amplifier stages due to its versatility in various applications.

The common emitter amplifier is widely used for its voltage amplification and current gain. It is very flexible in its design, allowing for different configurations based on the needs of the circuit. The common emitter amplifier is commonly used in audio and digital circuits and can be used in both linear amplification and switching applications.

Characteristics

Impedance
Input	Medium (dependent on biasing and resistor values)
Output	Medium to high

Gain
Voltage	Moderate to high (depending on the circuit design)
Current	High
Power	High (significant voltage and current gain)

Other Characteristics
Input/Output Phase Relationship	180 degrees out of phase (phase inversion)
Bandwidth	Limited by coupling and bypass capacitors

Typical Applications

General-purpose voltage amplifier
Audio amplification
Signal conditioning
High-gain amplification
Impedance matching (when coupled with a proper emitter resistor)
Oscillator circuits
Inverting amplifier for audio and RF applications
Amplification of small signals (e.g., sensors or microphones)
RF signal amplifiers
Signal amplification for communication systems

Common Collector Amplifier

The common collector amplifier gains its name from the fact that the collector is common to the input and output. It's normally called an emitter follower because the emitter follows the base voltage, although with a 0.6V difference due to the base-emitter junction voltage.

The common collector amplifier is widely used as a buffer stage due to its high input impedance and low output impedance, making it suitable for impedance matching. It does not amplify the voltage significantly but provides a high current gain and is very useful when you need to drive low-impedance loads while preserving the signal from a high-impedance source.

Characteristics

Impedance
Input	High (β times the emitter resistor)
Output	Low

Gain
Voltage	Close to 1 (no significant amplification)
Current	High
Power	Moderate (high current gain, low voltage gain

Other Characteristics
Input/Output Phase Relationship	In-phase (no phase inversion)
Bandwidth	Wide

Typical Applications

Buffer amplifier
Impedance matching
Voltage follower (emitter follower)
High-input impedance stage
Low-output impedance stage
Pre-amplifiers for low-power signals
Sensor interfacing circuits
Driving low-impedance loads
Power buffers in audio and video applications
Protection circuits for high-impedance sources
Signal isolation

Class AB Amplifier

The Class AB amplifier is a combination of Class A and Class B amplifiers, designed to provide higher efficiency than Class A while avoiding the crossover distortion of Class B. It operates in both positive and negative halves of the waveform but does not fully turn off during the negative half like in Class B. This results in improved efficiency without sacrificing too much in terms of linearity and distortion.

Class AB amplifiers are commonly used in audio applications due to their high efficiency and relatively low distortion. They are widely found in power amplifiers, audio amplifiers, and other high-power applications where maintaining good linearity and avoiding distortion is crucial.

Characteristics

Impedance
Input	Medium (dependent on the input stage configuration)
Output	Medium to high

Gain
Voltage	Moderate to high (provides a good balance between Class A and Class B)
Current	High
Power	High (combines high voltage and current gain with better efficiency than Class A)

Other Characteristics
Input/Output Phase Relationship	In-phase (no phase inversion)
Bandwidth	Wide (depending on the design and application)

Typical Applications

Audio power amplification
High-quality audio systems (e.g., home audio systems, car amplifiers)
Broadcast transmitters
Public address systems
Home theater audio systems
Musical instrument amplification
PA amplifiers in stadiums or events
Electroacoustic transducers (e.g., for speakers)

Common Base Amplifier

The common base amplifier is characterized by having the base as the common terminal for both the input and output. The input signal is applied to the emitter, and the output is taken from the collector. Unlike the common collector amplifier, the common base amplifier has a low input impedance but offers high voltage and current gain. It is primarily used in high-frequency applications and can provide a wide bandwidth.

The common base amplifier is often used when high-frequency response is critical, such as in RF amplifiers, or when a low-noise figure is required. It is commonly used in situations where the input impedance needs to be low, or the phase shift between input and output needs to be minimized.

Characteristics

Impedance
Input	Low (due to the emitter input impedance)
Output	High

Gain
Voltage	High (depending on the collector load and circuit design)
Current	Moderate
Power	Moderate to high (good voltage gain, moderate current gain)

Other Characteristics
Input/Output Phase Relationship	In-phase (no phase inversion)
Bandwidth	Narrow to medium (depending on frequency range)

Typical Applications

High-frequency amplifiers (e.g., RF applications)
Broadband amplifiers
Impedance matching in high-frequency circuits
Low-noise amplifiers in communication systems
Pre-amplifiers for RF signals
Voltage amplifiers for microwave frequencies
Amplifiers in radar systems
Low-noise front-end amplifiers in wireless communication
Mixers in RF and IF (intermediate frequency) systems
Analog signal conditioning in high-frequency applications
Amplifiers for measurement systems
Amplification of small high-frequency signals
Pre-amplifiers in analog communication devices
Oscillator circuits in high-frequency systems

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