Bjt amplifiers
- 1. D. Veera Vanitha Assistant Professor Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore, Tamil Nadu
- 2. Understand the concept of amplifiers Identify and apply internal transistor parameters Understand and analyze common-emitter, common-collector and common-base amplifiers
- 3. One of the primary uses of a transistor is to amplify ac signals. It has to be able to do it without distorting the original input.
- 4. The collector curves and load lines help us to relate the Q-point and its proximity to cutoff and saturation. The Q-point is best established where the signal variations do not cause the transistor to go into saturation or cutoff. For perfect amplifier Q- point must be in the middle of the active region.
- 5. The region between cutoff and saturation is called the linear region. A transistor which operates in the linear region is called a linear amplifier. Note that only the ac component reaches the load because of the capacitive coupling and that the output is 180º out of phase with input.
- 6. • The common-emitter amplifier exhibits high voltage gain and current gain. The output signal is 180º out of phase with the input signal.
- 7. Voltage gain -High Current gain - High Power gain - High Input or output phase relationship - 180 degree Input resistance - Low Output resistance -High
- 8. The common-collector amplifier exhibits high current gain and voltage gain is unity. The output signal is in phase with the input signal. It is also known as emitter-follower.
- 9. Voltage gain -Zero Current gain -High Power gain -Medium Input or output phase relationship - Zero degree Input resistance - High Output resistance -Low
- 10. • The common-base amplifier exhibits high voltage gain. The output signal is in phase with the input signal.
- 11. Voltage gain -High Current gain - Low Power gain -Medium Input or output phase relationship - Zero degree Input resistance - Low Output resistance -High