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Unity gain bandwidth (ωT) is the frequency at which the current gain of a common-emitter amplifier drops to unity (1). It represents the maximum frequency at which the transistor can provide amplification and is a key figure of merit for high-frequency performance.
The calculator uses the formula:
Where:
Explanation: The unity gain bandwidth is calculated by multiplying the common emitter current gain by the 3-dB frequency of the amplifier.
Details: Unity gain bandwidth is a critical parameter in amplifier design as it determines the maximum operating frequency of the transistor. Higher ωT values indicate better high-frequency performance and faster switching capabilities.
Tips: Enter the common emitter current gain (β) and the 3-dB frequency (fL) in hertz. Both values must be positive numbers greater than zero.
Q1: What factors affect the common emitter current gain?
A: The common emitter current gain is highly influenced by the width of the base region and the relative doping concentrations of the base and emitter regions.
Q2: How is 3-dB frequency measured?
A: The 3-dB frequency is the point at which the signal power is reduced to half (-3dB) of its maximum value, typically measured using frequency response analysis.
Q3: What are typical values for unity gain bandwidth?
A: Unity gain bandwidth values vary significantly depending on the transistor type, ranging from a few MHz for general-purpose transistors to several GHz for high-frequency devices.
Q4: How does temperature affect unity gain bandwidth?
A: Temperature changes can affect carrier mobility and junction capacitances, which in turn can influence both β and fL, thereby affecting the unity gain bandwidth.
Q5: Can this formula be used for all transistor configurations?
A: This specific formula applies to common-emitter configurations. Other configurations (common-base, common-collector) have different relationships between gain and bandwidth.