The d.c. analysis means to obtain the operating point values i.e. I Cq and V CEQ for the transistors used.

**D.C. Analysis of Differential
Amplifier**

The d.c.
analysis means to obtain the operating point values i.e. I _{C}q and V _{CEQ}
for the transistors used. The supply voltages are d.c. while the input signals
are a.c., so d.c equivalent circuit can be obtained simply by reducing the
input a.c. signals to zero. The d.c. equivalent circuit thus obtained is shown
in the Fig.. Assuming Rs_{1} = R _{S2}, the source resistance
is simply denoted by Rs ,

The
transistors Q1 and Q _{2} are matched transistors and hence for such a
matched pair we can assume :

i) Both the
transistors have the same characteristics.

ii) R _{E1}
= R _{E2} hence R _{E}= R _{E1}ll R _{E2}.

iii) R _{C1}
= R c _{2} hence denoted as R _{C}.

iv)lV_{CC}I
= lV_{EE} I and both are measured with respect to ground.

As the
two transistors are matched and circuit is symmetrical, it is enough to find
out

operating
point I _{CQ} and V _{CEQ}, for any one of the two transistors.
The same is applicable for the other transistor.

Apply-g
KVL to base-emitter loop of the transistor Q1

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Electronic Circuits : BJT Amplifiers : D.C. Analysis of Differential Amplifier |

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