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Low output impedance is important for low-impedance loads; for these loads, the voltage drop across the output impedance effectively reduces the open-loop gain. In configurations with a voltage-sensing negative feedback, the output impedance of the amplifier is effectively lowered; thus, in linear applications, op-amp circuits usually exhibit a ...
have large open-loop signal gain (voltage gain of 200,000 is obtained in early integrated circuit exemplars), and; have input impedance large with respect to values present in the feedback network. With these requirements satisfied, one can use the method of virtual ground to quickly and intuitively grasp the behavior of the op-amp circuits.
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.
Input and output impedances of a negative-feedback amplifier (closed-loop amplifier) become sensitive to the gain of an amplifier without feedback (open-loop amplifier)—that exposes these impedances to variations in the open-loop gain, for example, due to parameter variations or nonlinearity of the open-loop gain.
The output impedance is a measure of the source's propensity to drop in voltage when the load draws current, the source network being the portion of the network that transmits and the load network being the portion of the network that consumes. Because of this the output impedance is sometimes referred to as the source impedance or internal ...
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.
More generally, PM is defined as that of the amplifier and its feedback network combined (the "loop", normally opened at the amplifier input), measured at a frequency where the loop gain is unity, and prior to the closing of the loop, through tying the output of the open loop to the input source, in such a way as to subtract from it.
In electronics engineering, frequency compensation is a technique used in amplifiers, and especially in amplifiers employing negative feedback.It usually has two primary goals: To avoid the unintentional creation of positive feedback, which will cause the amplifier to oscillate, and to control overshoot and ringing in the amplifier's step response.