Op Amps

The inputs are high impedence, meaning it will not have a current draw on the input (except for gate leakage for a mosfet design), of course the amplifier still has a powersupply that will have current draw.

BJT amplifiers arent my thing but the nature of a bjt allows current flow into its base, so im thinking these amplifiers will have input current draw depending on the resistor on the base.

Virtual ground term is used in AC analysis, in a typical 5 transistor amplifier, where you have a current souce that then connects to 2 input fets, this node would be a virtual ground because though there is a DC voltage on this node, it is constant and so at an AC standpoint it is basically ground ( 0 signal change). There are more academic definitions out that you can can wiki or look up in a text book, but basically virtual ground is when the voltage is purely DC, when performing an AC analysis.

thanx dude