Figure 6.22, Two examples of grounded base amplifiers.

Part A is a typical IF amplifier that might be found in a table model AM/FM radio. In this figure plus 9 volts is at the top and minus 9 volts is at the bottom. Ground is in between but closer to the bottom than to the top. The circuit begins on the left with the same type IF transformer as used in figure 6.21. There are no connections to the primary. The top of the secondary connects to the emitter of the N P N BJT. The bottom of the secondary connects through a 9.1 k ohm resistor to minus 9 volts. The bottom of the secondary also goes through a 0.01 u f capacitor to ground. The base of the transistor is grounded. The collector goes to the bottom of the primary of another IF transformer. The primary tap goes to plus 9 volts. The tap also goes to ground through a 0.01 u f capacitor. The top of the primary is not connected. The secondary has no connections.

Part B is a typical FM RF amplifier that might be found in a portable or pocket AM/FM radio. Plus 9 volts is at the top and ground is at the bottom. The emitter of the transistor goes to the top of an inductor. The emitter also connects to an antenna. The bottom of the inductor goes to ground through the parallel combination of a 4.7 k ohm resistor and 0.01 u f capacitor. The base of the transistor goes to ground through the parallel combination of a 22 k ohm resistor and a 0.01 u f capacitor. The base also goes to plus 9 volts through another 22 k ohm resistor. Plus 9 volts is bypassed to ground by a 0.01 uf capacitor. The collector goes to the bottom of a transformer which schematically looks like an IF transformer but obviously is an FM RF transformer. The tap goes to plus 9 volts. The top is not connected. The secondary is shown not connected. End verbal description. Go back.