# Op-Amps Concept Clarification

• LickMyEyeball
In summary, the figure in "Microelectronic Circuits" shows internal independent current sources in an op-amp circuit. These sources, labeled as G_m, are voltage controlled current sources and are used to supply power needed by the op-amp. They are also known as gain multiplier values and have units of A/V. A more detailed explanation of transconductance and its relationship to G_m can be found in the provided Wikipedia link.

#### LickMyEyeball

I have been given a question regarding op-amps. In the figure however, there are elements which have not been introduced nor explained in the chapter. Please refer to the attached image.

(Image taken from "Microelectronic Circuits",by Sedra and Smith, 6th Ed., page 58.)

In the figure there are statements beside each internal independent current source. What is "G_m"? Are these current sources supplying power needed by the op-amp? Perhaps it is a part of gain? Can it be related to A?

I do not know. Any detailed conceptual explanation would be greatly appreciated, as I need to be able to use these values quantitatively and confidently!

Thanks for your time and patience.

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LickMyEyeball said:
I have been given a question regarding op-amps. In the figure however, there are elements which have not been introduced nor explained in the chapter. Please refer to the attached image.

(Image taken from "Microelectronic Circuits",by Sedra and Smith, 6th Ed., page 58.)

In the figure there are statements beside each internal independent current source. What is "G_m"? Are these current sources supplying power needed by the op-amp? Perhaps it is a part of gain? Can it be related to A?

I do not know. Any detailed conceptual explanation would be greatly appreciated, as I need to be able to use these values quantitatively and confidently!

Thanks for your time and patience.

The G_m are gain multiplier values. They have units of A/V, so they take a voltage as an input, and give you current as an output. Those are "voltage controlled current sources".

## 1. What is an op-amp?

An op-amp, short for operational amplifier, is an electronic component that amplifies the difference between two input voltages and outputs the result.

## 2. How does an op-amp work?

An op-amp is composed of multiple transistors and resistors that work together to amplify the input voltage. The op-amp has a high gain, meaning that even a small difference in input voltages can result in a large output voltage.

## 3. What are the main applications of op-amps?

Op-amps are commonly used in electronic circuits for signal conditioning, filtering, and amplification. They are also used in instrumentation and control systems.

## 4. What are the ideal characteristics of an op-amp?

An ideal op-amp would have an infinite gain, infinite input impedance, zero output impedance, and zero offset voltage. However, real op-amps have limitations and imperfections that must be considered in circuit design.

## 5. How do I choose the right op-amp for my circuit?

When choosing an op-amp, factors such as gain, bandwidth, input and output impedance, and power supply voltage must be considered. It is also important to consider the specific requirements of your circuit and any limitations of the op-amp being used.