_____________________________________________________________________ Special Amplifiers
R4
2=
R1
R4
4=
R2
R4
3=
R3
Any resistors that will provide the ratios shown above could be used. If the feedback
resistor (R4) is a 12-kilohm resistor, the values of the other resistors would be calculated as
follows:
12 kΩ
2=
R1
2(R1) = 12 kΩ
R1 = 6 kΩ
-------------
12 kΩ
4=
R2
4(R2) = 12 kΩ
R2 = 12 kΩ
-------------
12 kΩ
3=
R3
3(R3) = 12 kΩ
R3 = 4 kΩ
7-90. Figure 7-23 is the schematic diagram of a scaling amplifier with the values from
the previous calculations. To see if the circuit will produce the desired output, calculate the
currents and voltages as done for the previous circuits.
Figure 7-23. Scaling Amplifier
With:
E1 = +12 V
E2 = +3 V
E3 = +8 V
23 June 2005
TC 9-62
7-29
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