Input and output limits for OP amps

Source: Internet
Author: User

The op amp is powered by a dual supply and the output changes immediately following the input. A triangular wave with a amplitude of ±1.5v is added to the input to find the output clipping phenomenon, what is the cause of the problem?

To understand this problem, you need to know the common-mode input voltage (input voltage swing) and the output voltage swing.

1. Common-mode input voltage

When normal input is defined, the desired common-mode voltage range, common-mode input voltage is usually related to the power supply of the op amp. If this range is exceeded, the output signal will work in non-linearity, causing distortion;

2. Output Voltage Swing

Related to the OP amp power supply. Similarly, if this range is exceeded, the output signal is also distorted.

As shown in the following:

Note: We normally say that the rail-to-rail op amp, the common-mode input voltage can reach the power supply range, to reach the power supply of two rails, the output voltage close to the power rail.

First for the common-mode input voltage of 0V, working in its range, but the output is also 0V, not the output voltage swing range, so caused the output voltage may reach 200mV, causing a large error.

It can be analyzed that the input voltage is not within the common-mode input voltage range, so the output voltage may not be at the μv level and may answer the channel MV level.

Back to the beginning of the problem, the input is ±1.5v triangle wave, the output has a clipping phenomenon, the reason is that the input amplitude is not in the common-mode input voltage range. When the triangle amplitude value reaches 1.5V, it has exceeded the maximum value of 1V of the common mode input voltage, so it will produce clipping phenomenon;

Summary: For the use of op amp, it is necessary to consider whether the input voltage is in the common-mode input voltage range, but also to consider the output voltage swing problem.

Input and output limits for OP amps

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