Figure 5-12. Effect of Impedance Matching in the Coupling of Two Circuits

Solid State Devices and Solid State Power Supplies and Amplifiers
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TC 9-62

Figure 5-12. Effect of Impedance Matching in the Coupling of Two Circuits

IMPEDANCE CHARACTERISTICS OF AMPLIFIER CONFIGURATIONS

5-57. You have seen the importance of impedance matching the stages in an electronic

device. Next, we will look at the impedance characteristics of an amplifier. The input and

output impedances of a transistor amplifier depend upon the configuration of the transistor.

You have already been introduced to the CE, CB, and CC transistor configurations. Figure

5-13 shows examples of these configurations and their impedance characteristics.

NOTE: Only approximate impedance values are shown. This is because the

exact impedance values will vary from circuit to circuit. The impedance of any

particular circuit depends upon the device (transistor) and the other circuit

components. The value of impedance can be computed by dividing the signal

voltage by the signal current.

5-58. The CE configuration provides medium input impedance and medium output

impedance. The CB configuration provides low input impedance and high output

impedance. The CC configuration provides high input impedance and low output

impedance. The CC configuration is often used to provide impedance matching between

high output impedance and low input impedance.

5-14

TC 9-62

23 June 2005

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