3-33Figure 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 (E_{out}) should be:To see if this output (-50 V) is what the circuit will produce with the inputs given above, start bycalculating the currents through the input resistors, R1 and R2 (remember that point A is at virtualground):Next, calculate the current through the feedback resistor (R3):