### What is the significance of AC load line?

The ac load line is a graph that represents all possible combinations of  and  for a given amplifier. Under normal circumstances, the ac and dc load lines for a given amplifier are not identical. A typical ac and dc load line combination is shown in Figure 11-1a. Note that the two lines intersect at the circuit Q-point. The endpoints of the ac load line are defined as shown in Figure 11-1b. As shown, the ac saturation and cutoff points can be defined using circuit Q-point values.

It's Significance

•The ac load line of a given amplifier will not follow the plot of the dc load line.
•This is due to the dc load of an amplifier is different from the ac load.
•The ac load line is used to tell you the maximum possible output voltage swing for a given common-emitter amplifier.
•In other words, the ac load line will tell you the maximum possible peak-to-peak output voltage (Vpp ) from a given amplifier.
•This maximum Vpp is referred to as the compliance of the amplifier.
(AC Saturation Current  Ic(sat)  ,  AC Cutoff Voltage  VCE(off) )

### COMMON COLLECTOR CONFIGURATION OF A TRANSISTOR

COMMON COLLECTOR CONNECTION

In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by

COMMON COLLECTOR CIRCUIT

A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…