Example-1
Consider example-1 of lecture-2. The specifications are given again for the dual input, unbalanced-output differential amplifier: RC = 2.2 kΩ, RB= 4.7 kΩ, Rin1 = Rin2= 50Ω, +VCC = 10V, -VEE= -10 V, βdc =100 and VBE= 0.715V.
Determine the voltage gain, input resistance and the output resistance.
Solution:
Since the component values remain unchanged and the biasing arrangement is same, the ICQ and VCEQ values as well as input and output resistance values for the dual input, unbalanced output configuration must be the same as those for the dual input, balanced output configuration.
Thus, ICQ = 0.988 mA
VCEQ = 8.54 V
Ri1 = Ri2 = 5.06 kΩ
Ro = 2.2 kΩThe voltage gain of the dual input, unbalanced output differential amplifier is given by
Example-2
Repeat Example-1 for single input, balanced output differential amplifier.
Solution:
Because the same biasing arrangement and same component values are used in both configurations, the results obtained in Example-1 for the dual input, balanced output configuration are also valid for the single input, balanced output configuration.
That is,
ICQ= 0.988 mA
VCEQ = 8.54 V
Vd = 86.96
Ri = 5.06 kΩ
Ro1 = Ro2 = 2.2 kΩ