____________________________________________________________________________ Amplifiers
as coupling. There are various ways of coupling signals into and out of amplifier circuits.
The following is a description of some of the more common methods of amplifier
coupling.
Figure 5-7. Adding Stages of Amplification
Direct Coupling
5-37. This method uses the least number of circuit elements. Therefore, it is perhaps the
easiest to understand. In direct coupling the output of one stage is connected directly to the
input of the following stage. Figure 5-8 shows two direct-coupled transistor amplifiers.
5-38. Notice that the output (collector) of Q1 is connected directly to the input (base) of
Q2. The network of R4, R5, and R6 is a voltage divider used to provide the bias and
operating voltages for Q1 and Q2. The entire circuit provides two stages of amplification.
5-39. Direct coupling provides a good frequency response since no frequency-sensitive
components (inductors and capacitors) are used. The frequency response of a circuit using
direct coupling is affected only by the amplifying device itself.
23 June 2005
TC 9-62
5-9
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