electronics1 - vili.pmmf.huvili.pmmf.hu/~fuzi/electronics1/en1l06.pdf · multistage dc amplifier...
TRANSCRIPT
Electronics 1
Lecture 6
Multistage Amplifiers, Interstage Coupling, Feedback Tuned Amplifiers
Literature1. Tietze U, Schenk Ch: Electronic Circuits – Handbook for Design and Applications,
Springer, 2008, ISBN: 35400042972. Horowitz, Hill W: The Art of Electronics, Cambridge University Press, 1989,
ISBN: 0521370957
Coupling of amplifier stages
Direct coupling- both DC and AC components of the input signal are amplified- biasing of individual stages influence each other
Capacitive- only the AC components of the input signal are amplified- biasing of individual stages are independent
Inductive (via signal transformer)- only the AC components of the input signal are amplified- biasing design must take into account the fact that coils have very low DC resistance
Coupling of amplifier stages
Direct coupling- both DC and AC components of the input signal are amplified- biasing of individual stages influence each other
Differential common emitter common collectorinput stage voltage amplifier power stage
Multistage DC amplifier with direct coupling
Coupling of amplifier stages
Inductive (via signal transformer)- only the AC components of the input signal are amplified- biasing design must take into account the fact that coils have very low DC resistance
Class B push-pull amplifier with induvtive coupling
Class A amplifier with capacitive input and inductive output coupling
The principle of feedback
Negative series voltage feedback
Negative series voltage feedback
Two-stage common emitter amplifier with negative series voltage feedback
Negative series current feedback
Negative series current feedback
Common emitter amplifier without emitter resistance bypass
Tuned amplifiers Applied at high frequencies. Gain is strongly reduced out of the vicinity of the resonance frequency.Bandwidth: the limit of 3dB gain decrease.
Real oscillator circuit. Series-parallel equivalence
00 ps QQ
sp Cr
LR
Tuned amplifiersIn case of common emitter tuned amplifier the collector impedance is an oscillator circuit, therefore the gain is strongly frequency dependent.
gm 10…500 mS : transistor transconductance (DiC /DuB h21 / h11)1/h22 10…100 k : transistor output resistance1/h22 >> Rt
Coupling of tuned amplifier stages
Sinchronous tuning Staggered tuning
Coupling of tuned amplifier stages
Effect of coupling constant on a two-stage tuned amplifier
Oscillator circuit coupling
Coupling of tuned amplifier stages
The first mass production transistor radio receiver (1954)
Common base radiofrequency amplifier