08-16-2017, 09:16 PM
Common Emitter BJT Amplifier Design Current Mirror Design
[attachment=16721]
Some Random Observations
Conditions for stabilized voltage source biasing
Emitter resistance, RE, is needed.
Base voltage source will have finite resistance, RB.
needs to be much larger than RB.
Small RB - relative to RS - will attenuate input signal.
Larger RE permits larger RB, but results in lower gain.
Gain = -RC/RE for RE >> re.
Split RE with bypassing increases gain.
Requires large bypass capacitor.
Limiting case - entire RE bypassed: Gain = - gmRC.
Bias Setting
1. Since RB does not interfere with
the bias, the signal source can be
connected to the base without need
for a blocking capacitor.
2. Choose Rb large compared to
RS to avoid attenuating vsig.
3. Choose Rref to set IC
Gain Setting
1. Connect the source to the base.
2. Provide a path for the small
signal emitter current.
3. Choose RE for the desired gain
(G = - RC/RE).
4. CE is nearly a short circuit for f fmin
Calculate CE to have negligible
reactance at the lowest frequency
of interest fmin.