# Amplifier (OPAMP) General Summary

The subject of this article will be "Amplifier (OPAMP) General Summary". Thanks to this article, we will be able to learn about op-amps in general.

## Operational Amplifier General Conditions

- The Operational Amplifier, or Op-amp as it is most commonly called, can be an ideal amplifier with infinite Gain and Bandwidth when used in Open loop mode with typical DC earnings well above 100,000 or 100dB.
- The basic Op-amp structure is a 3-terminal device with 2 inputs and 1 output (excluding power connections).
- The Operational Amplifier operates either from a double positive ( +V ) and the corresponding negative ( -V ) source, or it can operate from a single DC supply voltage.
- There are two main laws concerning the transactional amplifier. It has an infinite input impedance ( Z = ∞ ). No current flows into any of its two inputs, and the zero input offset voltage results in V1 = V2.
- The transactional amplifier also has zero output impedance ( Z = 0 ).
- Op-amps detect the difference between voltage signals applied to the two input terminals and then multiply this by a predetermined Gain (A).
- This Gain, ( A ) is often referred to as amplifiers "Open loop Gain".
- Closing the open loop by connecting a resistant or reactive component between the output of the Op-amp and an input terminal greatly reduces and controls this open-cycle gain.
- Op-amps can be connected to two basic configurations, inverting and inverting.

## Two Basic Operational Amplifier Circuits

- For negative feedback, if the feedback voltage is "anti-phase" to the input, the overall gain of the amplifier is reduced.
- For positive feedback, if the feedback voltage is in "Phase" with input, the overall gain of the amplifier increases.
- By connecting the output directly to the negative input terminal, 100% feedback is obtained resulting in a Voltage Tracker (buffer) circuit with a constant gain of 1 (Union).
- By changing the constant feedback resistance (Rε) for a Ponsiometer, the circuit will have Adjustable Gain.

## Operational Amplifier Gain

- Open loop gain, called Gain Bandwidth Product or (GBP), can be very high.
- Very high GBP makes the operational amplifier circuit unstable as the micro volt input signal causes the output voltage to turn into saturation.
- With the use of an appropriate feedback resistance (Rε), the overall gain of the amplifier can be accurately controlled.

## Differential and Total Risers

- Voltage Collectors or differential receivers can be made by adding greater input resistance to inverter or non-inverter inputs.
- Voltage tracker op-amps can be added to the inputs of differential amplifiers to produce high impedance instrumentation amplifiers.
- The differential amplifier produces an output proportional to the difference between the two input voltages.

## Derivative and Integral Receiving Transactional Amplifier Circuits

- The Integral Receiver Amplifier produces an output that is the mathematical process of integration.
- The Derivative Receiver Amplifier produces an output that is the mathematical process of differentiation.
- Both Integral Receiver and Derivative Receiver Amplifiers have a resistance and capacitor connected throughout the op-amp and are affected by the RC time constant.
- In basic forms, Derivative Receiver Amplifiers suffer from instability and noise, but additional components can be added to reduce overall closed loop gain.