3-33
Figure 3-23.—Summing amplifier.
If this circuit is designed correctly and the input voltages (E1 and E2) are +2 volts and +3 volts,
respectively, the output voltage (Eout) should be:
To see if this output (-50 V) is what the circuit will produce with the inputs given above, start by
calculating the currents through the input resistors, R1 and R2 (remember that point A is at virtual
ground):
Next, calculate the current through the feedback resistor (R3):
