_____________________________________________________________________ Special Amplifiers
is considered to be virtual ground. Remember, in a closed-loop operation the inverting and
noninverting inputs are at the same potential.
7-60. Virtual ground is a point in a circuit that is at ground potential (0 volts) but is not
connected to ground. Figure 7-13 shows an example of several circuits with points at
virtual ground. In view (A), V1 (the left-hand battery) supplies +10 volts to the circuit
while V2 (the right-hand battery) supplies -10 volts to the circuit. The total difference in
potential in the circuit is 20 volts.
Figure 7-13. Virtual Ground Circuits
The total resistance of the circuit can be calculated as follows:
RT = R1 + R2
RT = 1Ω + 1Ω
RT = 2Ω
23 June 2005