# Op Amp Circuits

### - overview of the various op amp circuits that can be designed, developed and used.

Op-amp circuits include:

• Operational amplifier circuits

• Inverting op-amp

• Non-inverting op-amp

• Op-amp high pass filter

• Op-amp low pass filter

• Op-amp bandpass filter

• Op-amp variable gain amplifier

• Op-amp notch filter circuits

• Operational amplifier multivibrator

• Op-amp bistable

• Op-amp comparator

• Op-amp Schmitt trigger

• Op-amp integrator

• Op-amp differentiator

Operational amplifiers or op amps can be used in a wide variety of different analogue circuits.

The basic op amp integrated circuit, makes them an almost ideal circuit building block which can be used to provide exceedingly high levels of performance.

Typically an operational amplifier circuit requires a few external components to make a high performance analogue circuit.

It is the high gain of the basic amplifier combined with the use of feedback (most often negative feedback) that enables the final circuits to provide such a high level of performance.

## Op amp circuits

The list below provides links to a variety of commonly used op amp circuits. These circuit range from simple linear amplifiers, to filters, variable gain amplifiers, a-stables and bi-stables and more.

The inverting amplifier is one of the most commonly used. It is simple requiring just a few additional resistors to provide a highly effective amplifier. It can also be used as a virtual earth mixer, combining several audio inputs together. The inverting amplifier has a low input impedance and a low output impedance.*Inverting amplifier:***Read more about the Inverting op-amp**The non-inverting amplifier is another popular circuit. It is often just a little more complicated than the inverting format, but has a very high input impedance while maintaining a low output impedance.*Non-inverting amplifier:***Read more about the Non-inverting op-amp**High pass filters can be used in many applications. One instance where a high pass filter may be used is to remove unwanted low frequency noise such as mains hum.*High pass filter:***Read more about the Op-amp high pass filter**Low pass filters are very useful and can be used to remove the unwanted high frequency elements of a signal.*Low pass filter:***Read more about the Op-amp low pass filter**Band pass filters can be made quite easily using op amps. While the upper frequencies can be limited, they are ideal for audio and many other applications.*Bandpass filter:***Read more about the Op-amp bandpass filter**This op amp circuit enables the gain of the amplifier to be controlled using a single resistor.*Variable gain amplifier:***Read more about the Op-amp variable gain amplifier**Notch filters are widely used in removing a single frequency from a spectrum. For op amp notch filters that will tend to be used more within the audio spectrum, these notch filters could be used for removing mains hum, or for removing or accepting specific tones.*Notch filter:***Read more about the Op-amp notch filter circuits**Multivibrators are a commonly used in many areas of electronics. An op amp multibrator may be used where a simple oscillator is needed in an analogue circuit.*Multivibrator:***Read more about the Operational amplifier multivibrator**It is sometimes convenient to have a bi-stable made from op amps. This circuit shows how this can be done very easily.*Bistable:***Read more about the Op-amp bistable**This circuit shows how a comparator can be made using an op amp. Strictly speaking a comparator chip rather than an op-amp should be used as you will find out.*Comparator:***Read more about the Op-amp comparator**The Schmitt trigger is a very popular circuit. Introducing some hysteresis into the switching, this reduces the effects of noise and enables solid switching to be achieved.*Schmitt trigger:***Read more about the Op-amp Schmitt trigger**

## Op amp circuit design considerations

When designing operational amplifier circuits there are several design considerations that need to be remembered. Various aspects of op amp circuit design are common to most circuits if not all.

Some of the basic concepts about basic op-amp design.*Basic op amp circuit design:***Read more about Op amp basics**Operational amplifiers have very high levels of gain when operated in open loop. The final level of gain is very much less when negative feedback is applied. Knowing about the gain, and how to use it to obtain the best results is a key factor in op-amp circuit design.*Op-amp gain:***Read more about Op amp gain**

* By Ian Poole*

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