4–95 Bipolar Power Supply Voltages The circuit in Figure P4–95 produces bipolar power supply voltages VPOS > 0 and VNEG 0. Note that the OP AMP output is grounded and that its +VCC and −VCC terminals are connected to VPOS and VNEG, respectively.

(a) Show that VPOS = +VREF=2 and VNEG = −VREF=2 even if the load resistors RPOS and RNEG are not equal.

(b) If RPOS and RNEG are not equal, a current iG must flow into or out of ground. How does the ungrounded voltage source VREF supply this ground current?

(c) In effect, the OP AMP creates a “virtual ground” at point A ðVA = 0Þ but draws no current in doing so. Why not just connect point A to a “real ground” and do away with the OP AMP?

Transcribed Image Text:

+ VREF R VI A Vcc V2 Vpos RpoS iG io + R -Vcc RNEG VNEG FIGURE P4-95