Provides voltage gain with phase inversion.
The CE stage gives voltage gain A_v≈-g_m R_C (≈-R_C/r_e) with 180° phase inversion, moderate input and high output impedance. Emitter degeneration trades gain for linearity and stability. Capacitors couple AC and bypass the emitter resistor.
With I_C=1 mA, R_C=4.7 kΩ gives gain around -180.
The common-emitter stage gives voltage gain, and it is the most common single-stage amplifier used in analogue electronics.
Provides voltage gain with phase inversion.
The common-emitter stage gives voltage gain, and it is the most common single-stage amplifier used in analogue electronics.
An increase in input voltage raises the base current and collector current, which lowers the collector voltage through the load resistor, so the output is inverted.
The transistor's transconductance and the load resistance set the gain, and an emitter resistor reduces it while improving stability.
Typical applications include amplifying a sensor signal before an ADC, building a gain stage in a radio receiver front end and designing a preamplifier for a microphone input.
Study "Transistor as a switch" first (topic 11 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
g_m=I_C/V_T. Miller effect limits bandwidth. Common-collector gives buffering.
With I_C=1 mA, R_C=4.7 kΩ gives gain around -180.
The next topic is "MOSFET", which builds directly on this one.
It is classed as Beginner in Electronics & Embedded (topic 12 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.