0 volt reference
The main parameter responsible for virtual ground of an Op-Amp is Input Impedance . Generally , for an Op-Amp it is very high . So , we can conclude that the characteristics of an Op-Amp responsible for virtual ground is high input impedance .
An op amp must remain in its active region for virtual ground to be preserved.
Ordinary ground is a simple connection to ground. Virtual ground is an op-amp's response to maintaining a reference point in the bridge with respect to an ordinary ground. This is why an op-amp makes a nearly ideal mixer - it allows you to sum multiple inputs together with little or (nearly) no cross-talk. (Limitations, of course, being based on CMRR and frequency response.)
VIRTUAL GROUND:-1]If the non-inverting (+) terminal of OP-AMP is connected to ground, then due to the "virtual short" existing between the two input terminals, the inverting (-) terminal also be at ground potential. hence it is said to be as "virtual ground".2]similarly if the inverting (-) terminal is connected to ground, then the non- inverting (+) terminal will be at "virtual ground" potential.3]The concept of virtual ground has been used extensively for amplifier analysis, specially we use this concept in the inverting amplifier.VIRTUAL SHORT:-1] The input impedance (Ri) of an OP-AMP is ideally infinite. Hence current "I" flowing from one input terminal to the other will be zero.2] Thus the voltage drop across Ri will be zero and both input terminals will be at the same potential. In other words they are virtually shorted to each other.
Virtual ground is a point in the circuit that is maintained at some known reference, such as ground, without actually being connected to it. This is commonly the junction of the resistor divider between input and output at the negative input pin, while the positive input pin is grounded (usually through a resistor). The op-amp maintains this virtual ground by making the output be whatever it takes to rebalance the input divider. Zero point is the half-way point between the two power supply pins. With a normal op-amp configuration running at +15 and -15, the zero point is ground. With a single ended configuration, such as +5 and ground, the zero point is 2.5 volts. It represents the mid point that the op-amp is capable of producing.
A: They both use transistors. In actuality before an op amp becomes an op amp a discrete transistor made is made to provide it capabilities before it gets integrated into a substrate chip we call op amp. OP AMP have two input to work as a differential amplifier the input are bases closely match to provide virtual no voltage or current offset. Single ended amplifier has one input its reference is the signal source return.
if non inverting terminal is grounded and input is applied to inverting terminal then as the difference in input voltage should be ideally zero the potential at inverting terminal is also assumed to be zero
since an op-amp has very high open loop gain, the potential difference b/w its inputs tend to zero when a feedback n/w is implemented.to acheive a reasonable voltage at the output and thus equilibrium in the system,the output supplies the inverting input with enough voltage.the inverting input although not connected to ground,will assume a similar potential ,becoming a VIRTUAL GROUND...
When the magnitude of Vcc and Vee of op-amp are different the op-amp produces waveforms equal in the size of each rail.
A basic, single transistor amplifier differs from an op amp: 1. The op amp has more gain 2. The op amp may have higher input resistance (so it loads the circuit less) 3. The op amp may have a lower output resistance (so it can drive larger currents) 4. The op amp likely has a lower frequency response (due to the high gain, unless you provide some sort of feedback loop) 5. The op amp is ridiculously complex compared to a simple amplifier 6. The op amp will require a positive and negative voltage (may be unnecessary with a single transistor amplifier)
Feedback in used in an op-amp to limit and control the gain. An op-amp, by itself, has very high gain, often more than 100,000. (A theoretical op-amp has infinite gain.) The external feedback loop forms a divider, more correctly a bridge, that is maintained in balance by the op-amp, giving the desired real gain.
op-amp