Skip to main content

Select preferred language from 'Translate' hidden side menu =>

Blog Navigation

By
                              Blog Navigation 
Post a Comment

Why does a circuit need positive and negative?

Image
By

 Purpose of Dual Power Supply in Analogue Circuit Design: Why Positive and Negative Voltages Matter

Look at the following two circuits…

A Push-Pull audio single-ended Amplifier: 

Audio Push-Pull Amplifier with single ended power supply

   Push-Pull Audio Amplifier with dual Power Supply:

Audio amplifier with duel power Supply

What is the difference between the two above circuits?

In the second circuit, there is an absence of an output coupling capacitor.

Why is a capacitor needed in the first circuit? It charges at a positive cycle and discharges at a negative cycle, generating an AC voltage across the speaker.

In the second circuit, at the positive input cycle, current flows to the speaker. At a negative input cycle, current is pulled from the negative supply through the speaker, thus eliminating the output capacitor.

The output coupling capacitor has a few disadvantages. It puts a limit on low-frequency response, it is bulky, and needs a high value for better low-frequency response; it may dry out, and needs a replacement after a certain period.

Conclusion: positive and negative supply is needed in a high-end, direct-coupled amplifier circuit that eliminates coupling capacitors.


Affiliate Link

🔹 FAQ Set:

Q1. Why do analogue circuits require both positive and negative voltages?

Analogue circuits often handle signals that swing above and below zero volts. Dual supplies (+V and –V) allow amplifiers to process AC signals symmetrically without distortion.

Q2. Can a circuit run on only one positive voltage?

Yes, but it limits signal range. Single-supply designs need biasing to shift the reference to mid-voltage, reducing dynamic range and accuracy.

Q3. What is the advantage of using dual power supplies in op-amp circuits?

Dual power supplies simplify biasing, enable true zero-volt output, and improve linearity for AC and DC signal amplification.

Q4. Can we use two negative voltages instead of one positive and one negative?

Not typically. Circuits depend on a common ground reference; using two negative rails without a positive reference can cause incorrect biasing.

Q5. Which applications mostly need dual-polarity power supplies?

Audio amplifiers, analogue signal processing, instrumentation amplifiers, and sensor interfaces often require ±12V or ±15V dual supplies.


More content like this: 

If you like my content, consider supporting us:

Gpay Support Link






Comments

Post a Comment

Popular Posts

Blog Navigation

By
                              Blog Navigation 
Post a Comment
Read more

Why does AC current change direction?

By
Why Does AC Current Reverse Direction Periodically? Understanding Alternating Current generation, Frequency, and Working Principle of an AC generator The answer to this question goes back to the generator where AC power is generated. A simple voltage generator:  Imagine a simple loop of coil is rotating between the two strong magnetic bars. 0 to 180 degrees,i.e. Half rotation. You will notice that when the coil is perpendicular to the magnetic field, its output is minimum or zero due to the minimum linkage of the magnetic field. But as the coil rotates to become parallel to the magnetic field, its output increases and becomes maximum when it is parallel. 180 to 360 degrees, i.e. Full rotation. The same cycle repeats, but now the voltage is negative. The following diagram explains it. Hence, as the AC voltage reverses its polarity periodically, the load current will also change direction of flow periodically. AC current direction: FAQ Set: Q1: Why does AC current reverse direction p...
Post a Comment
Read more

Why are transformers rated in VA and not watts?

By
Why Is Transformer Rating Given in VA? Understanding Power in Volt-Ampere versus watts, Power Factor, and Transformer Efficiency related to inductive load Real reason: Because the manufacturer of the transformer never knows where it is going to be used. Suppose a transformer of 100KVA feeds a resistive load; it will develop 100 kilowatts of power across the load because the power factor of the resistive load is unity. If the same transformer feeds an inductive load of power factor 0.5, then it will develop only 50 kilowatts of power across the load. Hence, if I want to rate a transformer in watts, then I need to know the power factor of the load, which is impossible. So, the transformer is rated in VA, KVA or MVA. A mug of beer analogy of Power Factor: FAQ Set: Q1: Why is transformer rating given in VA instead of watts? Transformer ratings are given in   VA (volt-amperes)   because transformers must handle   apparent power , which includes both real power (watts) and reac...
Post a Comment
Read more