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An operational amplifier (often op amp or opamp) is a DC-coupled electronic voltage amplifier with a differential input, a (usually) single-ended output, [1] and an extremely high gain. Its name comes from its original use of performing mathematical operations in analog computers .
Like a standard operational amplifier, the OTA also has a high impedance differential input stage and may be used with negative feedback. [3] But the OTA differs in that: The OTA outputs a current while a standard operational amplifier outputs a voltage. The OTA is usually used "open-loop"; without negative feedback in linear applications.
The open-loop gain is a physical attribute of an operational amplifier that is often finite in comparison to the ideal gain. While open-loop gain is the gain when there is no feedback in a circuit, an operational amplifier will often be configured to use a feedback configuration such that its gain will be controlled by the feedback circuit components.
Such is the case with the operational transconductance amplifier, which has an open-loop gain (transconductance) in siemens , because the gain is a ratio of the output current to the input voltage. Example
The operational amplifier integrator is an electronic integration circuit. Based on the operational amplifier (op-amp), it performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.
In this case, an external push–pull amplifier can be controlled by the current into and out of the operational amplifier. Thus, the operational amplifier may itself operate within its factory specified bounds while still allowing the negative feedback path to include a large output signal well outside of those bounds. [1]
The current-feedback operational amplifier (CFOA or CFA) is a type of electronic amplifier whose inverting input is sensitive to current, rather than to voltage as in a conventional voltage-feedback operational amplifier (VFA). The CFA was invented by David Nelson at Comlinear Corporation, and first sold in 1982 as a hybrid amplifier, the CLC103.
The reason is that many practical factors can reduce the phase margin below the theoretical minimum. A prime example is when the amplifier's output is connected to a capacitive load. Therefore, operational amplifiers are usually compensated to achieve a minimum phase margin of 45° or so. This means that at the frequency at which the open and ...