LM4558 Dual Operational Amplifier

LM4558 IC is a monolithic integrated chip consisting of two operational amplifiers that belong to the LM series of integrated circuits. Although these two operational amplifiers reside in a single package, but they operate independently of each other. However, both operational amplifiers share the same power rails. The two op-amps have very low noise interference among them which makes LM4558 ideal for use in a number of applications.

LM4558 Pinout

LM4558 pinout        

Pin Description

It consists of two operational amplifiers inside a single package.

Operational Amplifier 1

  • Pin2: Positive Input pin
  • Pin3: Negative Input pin
  • Pin1: Output

Operational Amplifier 2

  • Pin5: Positive Input pin
  • Pin6: Negative input pin
  • Pin7: Output pin

Pin8 and 4 are voltage supply pins. Connect these pins to voltage supply and ground.

Features

It provides the following features:

  • It provides a single supply operation in a range of +5.0 V to +15 V and dual supply range lies in between +15V and -15V.
  • This device is latch-up proof.
  • Internal compensation, therefore, external frequency compensation is not needed.
  • Consumes very low power which makes it suitable for so many applications
  • Provides matching phase and gain between the amplifiers
  • The total power dissipation is 200 mW.
  • It consists of low noise transistors at the input.
  • It provides continuous protection against short circuits.
  • The Common-Mode Rejection Ratio is 80dB.
  • The IC operates in a range of 0 °C to 70 °C.

Where to use it?

LM4558 IC possesses a wide range of common-mode input voltage and differential voltage. In addition to that, it provides a latch-up free operation. You don’t need to connect external components for frequency compensation. It has a built-in frequency compensation which provides stable operation. These features make this device well suited for amplification processes and voltage follower applications.

How to use it LM4558?

The two op-amps inside the chip can perform two different functions at the same time. As mentioned in the above section, this dual amplifier IC is well suited for voltage following applications. Therefore, we will explain this circuit to understand its working.

internal op amp structure

Voltage Follower Circuit Example

A voltage follower has nothing to do with amplification. It is just like a buffer and outputs the input value as it is. If the load attached to the output has low resistance, it will draw more current. Here comes the advantage of an operational amplifier.

They provide high impedance due to which load draws a very small amount of current. Due to their high impedance, they do not load down the source connected at the input pin. As the inverting input is directly connected to the output pin without any resistor in between them, that’s why it generates the same input value at the output pin.

LM4558 voltage follower circuit example

Multivibrator Circuit Example

It can produce its own input signal with the help of a resistor and capacitor network connected as feedback between inverting input and output pin. Connect a voltage divider between the non-inverting and output terminal. The circuit will behave as a multivibrator and generates rectangular pulses. Figure (4) shows the circuit of a multivibrator.

LM4558 multivibrator circuit example

Equivalents and Alternatives

LM4558 Applications

This versatile IC is useful in many applications. Few of them are:

  • Performs mathematical operations like integration, differentiation, sum, etc.
  • It provides very low distortion and hence employed in sine wave oscillator circuits and phase shift oscillators.
  • Signal Processing and filtering, Peak Detectors, Multivibrators, instrumentation are all its applications

2D Diagram

It is found in 8 pin SOP and 8 pin DIP-packages. The figure shows the two-dimensional diagram of the 8-pin DIP package. The dimensions are in inches. The values in brackets are in millimeters.

LM4558 Datasheet

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