27-03-2014, 11:05 AM
INTRODUCTION OF OPERATIONAL AMPLIFIER AND ITS CHARACTERISTICS
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OPERATIONAL AMPLIFIER
An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp produces an output voltage that is typically hundreds of thousands of times larger than the voltage difference between its input terminals.
An operational amplifier (or an op-amp) is an integrated circuit (IC) that operates as a voltage amplifier. An op-amp has a differential input. That is, it has two inputs of opposite polarity. An op-amp has a single output and a very high gain, which means that the output signal is much higher than input signal.
These amplifiers are called "operation" amplifiers because they were initially designed as an effective device for performing arithmetic operations in an analog circuit. The op-amp has many other applications in signal processing, measurement, and instrumentation.
CHARACTERISTICS OF AN IDEAL OP-AMP
Open-Loop Voltage Gain - Voltage gain is defined as the ratio of output voltage to an input signal voltage. It is denoted by A0L. The value of this infinite.
Output Impedance – This is denoted by R0 and is zero for an ideal op-amp. This ensures that the output voltage of the op-amp remains same , irrespective of the value of the load resistance connected.
Input Impedance – This is denoted by Rin and is infinite for an ideal op-amp. This ensures that no current can flow into an ideal op-amp.
PSRR - The power-supply rejection ratio PSRR is the ratio of the change in input offset voltage to the corresponding change in one power-supply, with all remaining power voltages held constant. The PSRR is also called "power supply insensitivity". Typical values are in :V / V or mV/V. It is 0 for an ideal op-amp.