Electronic Basics #21: OpAmp (Operational Amplifier)

Summary

This video introduces operational amplifiers (op-amps), explaining their common usage in analog and digital electronics. The presenter demonstrates how to use the LM358 dual op-amp, covering basic concepts such as voltage input, voltage dividers, and amplification factors. The video also highlights the limitations and practical considerations when using op-amps, including DC offset, supply voltage limitations, and the importance of feedback in different configurations like inverting and non-inverting amplifiers. The video concludes by encouraging viewers to explore further applications and reminding them to like, share, and subscribe.

Takeaways

• 🔍 Operational amplifiers (op-amps) are commonly used in both analog and digital electronics for various applications.
• 🛠️ Op-amps can be found in dual inline packages with 14 pins featuring four op-amps, or in 8-pin packages with one or two op-amps.
• 🔌 The LM358 is a popular op-amp that can operate with a single supply voltage, as demonstrated in the script.
• ⚙️ The first golden rule of op-amps is that they attempt to maintain zero voltage difference between their inputs.
• 🔢 The gain of a non-inverting op-amp circuit can be calculated using the voltage divider formula and the input voltage.
• 📡 Op-amps can amplify signals from sensors like PT100 temperature sensors or AC signals from electret microphones.
• 🚫 The output voltage swing of an op-amp is limited by the supply voltage, which can restrict the amplification of AC signals.
• 🔄 Adding a DC offset to the input can help in amplifying AC signals without exceeding the supply voltage limits.
• 🚫 Ideal op-amps have infinite input impedance and zero output impedance, but real-world op-amps have non-ideal parameters.
• 🚀 Red rail op-amps can achieve an output voltage equal to their supply voltage, which is useful for certain applications.
• 🔄 Inverting op-amp circuits are suitable for amplifying AC signals from sources like microphones without amplifying DC components.
• ⚠️ Without feedback, an op-amp can act as a comparator with high open-loop gain, jumping to maximum or minimum output voltage based on input differences.

Q & A

What is an operational amplifier commonly referred to as?

An operational amplifier is commonly referred to as an 'op-amp'.

What is the purpose of an op-amp in electronic circuits?

Op-amps are used for amplifying signals, performing mathematical operations, and filtering in both analog and digital electronics.

What are the common package types for op-amps?

Op-amps can be found in dual inline packages (DIP) with 14 pins, featuring four op-amps, or in 8-pin packages, featuring two or one op-amp.

Which op-amp model is used as an example in the script?

The LM358 is used as an example of an op-amp in the script.

What is the golden rule of op-amps regarding the voltage difference between the inputs?

The first golden rule of op-amps states that the output of an op-amp will always attempt to keep the voltage difference between the inputs at zero volts.

How can the gain of a non-inverting op-amp circuit be calculated?

The gain of a non-inverting op-amp circuit can be calculated using the formula: gain = 1 + (R2 / R1), where R1 and R2 are the resistors in the voltage divider.

What is the issue with amplifying an AC signal without a DC offset?

Amplifying an AC signal without a DC offset results in only the positive AC voltage being amplified because the output voltage swing is limited to the supply voltage.

What is the solution to amplify an AC signal completely without amplifying any DC voltage?

A solution is to use an inverting op-amp configuration and connect the positive input to a DC offset voltage instead of ground.

Why are the sound levels almost inaudible when connecting the output of an op-amp to a speaker?

The sound levels are almost inaudible because of the small maximum output currents that op-amps can provide.

What is the function of a comparator in op-amp circuits?

A comparator is used when no feedback is attached between the output and input of an op-amp, causing the output to jump to the maximum or minimum output voltage based on the input voltage difference.

What are some of the non-ideal parameters of an op-amp that are mentioned in the script?

Some non-ideal parameters mentioned include finite high input impedance, non-zero output impedance, and the inability to achieve an output voltage equal to the supply voltage.

What are 'red rail' op-amps and what is their special characteristic?

'Red rail' op-amps are a type of op-amp that can achieve an output voltage that equals their supply voltage, overcoming the limitation of non-ideal op-amps.

What are the three golden rules of op-amps mentioned in the script?

The script does not explicitly list three golden rules, but it discusses the importance of maintaining zero voltage difference between inputs, the use of feedback for gain calculation, and the behavior of op-amps as comparators when no feedback is present.