Electronics FAQ – Your Multilingual Guide to Electronics

Importance of a current-limiting resistor in an LED circuit LED is basically a forward-biased diode: Like a revered biased zener, it has a fairly constant voltage drop of 1.5V to 3V. If you supply more than this voltage, even slightly more, a large current will flow through it, as there is no mechanism to absorb the excess voltage (LED - supply). Result: LED damage from overcurrent. Mechanism of current limiting resistor:  A resistor in series absorbs the voltage difference and sets a safe current through it. A series resistor also has a secondary purpose of setting the light intensity of the LED. Especially in a battery powered gadgets, it is important to conserve battery.

  How a VFD Converts AC to DC | VFD Working Principle Explained | AC to DC Conversion in Variable Frequency Drives | Power Electronics Basics Need for AC to DC conversion in VFD:  By doing this, the VFD drive kills two birds with one stone, i.e. frequency control and voltage control. Induction motor speed control requires two major things… Frequency control Voltage control AC is converted to DC. This can be done by a single-phase or a three-phase AC input supply. E.g. arrangement of a single-phase inverter. Frequency control :  DC is inverted to variable frequency three-phase AC. To reduce harmonics,  the  PWM   technique is used to generate a sinusoidal current through the induction motor. Voltage control :  Alone, changing frequency to control the speed of the induction motor is not enough because when the speed changes, back emf also changes. At low speed, back emf is reduced, and the motor draws more current, which heats up the motor.   Voltag...

  Why the Voltmeter is Connected in Parallel and the Ammeter in Series | Explained with Illustrations Measurement principle: Ideally, a measuring instrument must not alter the reading being measured. Loading effect of measuring instruments:  What does it mean? E.g. a voltmeter must not load the (voltage) source to alter the actual reading. The above circuit shows how a reading by the voltmeter is altered due to the loading effect as the input impedance of the voltmeter comes in parallel to the load. Open circuit voltage measurement:  Another example is measuring the open-circuit voltage with a voltmeter. The internal resistance of the battery or voltage source and the input impedance of the voltmeter form a voltage divider. That will decrease the actual voltage being measured. Why a voltmeter must have a high input impedance:  The input impedance of the voltmeter becomes critical for the voltage sources that have high internal impedance. For example, various process ...

Digital Volume Control in Modern Audio Amplifiers. What is the principle of a Digital Potentiometer and its role in audio amplifiers?  We all know antic audio amplifiers use analogue potentiometers. They become noisy due to dust and require frequent cleaning. Modern amplifiers use digital volume control, though the volume control knob looks the same, the circuit for the same is entirely different. It uses fixed resistors in a voltage divider configuration and switches them electronically to control volume. This is done in digital volume control. Digital volume control module:  Modern audio amplifiers no longer use an analogue potentiometer to control volume. How does volume control work in Audio Amps? The volume control knob of an audio amplifier is essentially a voltage divider. Voltage Divider principle:  The output of the pre-amp is scaled and given to the power amp. And this scaling is done by analogue potentiometer by turning the volume control knob of the amp. Digit...

  How RC Low-Pass and High-Pass Filters Work — Simple Explanation with Examples Let me provide you with a basic understanding that will clear up any misunderstandings you may have regarding the capacitor in a high/low-pass filter. Mechanism of High/Low Pass Filter: ‘Filter’ word is a bit misleading. It doesn’t take ON/FF-type action. Filter only reduces (voltage) gain for a certain frequency compared to the whole spectrum of the frequencies of interest. A filter is basically a Voltage Divider:  The filter works on a voltage divider principle. Let me clarify. So, the output voltage reduces proportionally to the value of resistors R1 & R2. In simple words, the larger the R1 and the smaller the R2, Vout will reduce compared to Vin. Can I use the above circuit as a low-pass filter? No, because resistance doesn't change its value proportionally to the frequencies . So our goal of reducing gain for a certain band of frequencies wont be fulfilled. We need to replace R1 or R2 with...

  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:     Push-Pull Audio Amplifier with dual 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: ...

Voltage Regulator vs Current Regulator: Definition, Working Principle, Circuit, and Key Differences in Electronics A word ‘regulator’ means control, similar to the gas flow control in our home gas stove. That way, the word ‘voltage/current regulator’ is a bit of a misnomer. The correct wording is ‘Automatic Voltage/Current Regulator’. However, I will use the word' voltage regulator in place of ‘Automatic voltage regulator’ in the following answer. Voltage/Current regulator definition:  Voltage/Current regulator keeps the voltage/current level at the predetermined level within a narrow tolerance band with respect to the input and load variations. Coming back to the OP’s question, the following is the feedback control diagram of the regulator. Voltage regulator block diagram: The principle of operation is very simple. The sampled output voltage is compared with the reference voltage set by the zener diode. Any error is nullified by a control element, which absorbs the differace in vo...

What is DC Bias Voltage used in Electronic circuits? — Definition, Importance & Practical Examples DC bias is simply a deliberate addition of a DC voltage to a (circuit) node to offset its operating voltage level. Voltage divider bias in a common emitter amplifier:  The most common and popular example of DC bias is the voltage divider bias in a common-emitter amplifier. What will happen if the DC bias is not given to the base of the above circuit? The transistor will act like a rectifier; it will amplify only the positive part of the signal, creating a distorted output that we don't want. Purpose: The purpose of the DC bias in the above circuit is to keep the base DC offset voltage sufficiently high to keep the base-to-emitter junction forward-biased all the time, considering the subtractive effect of the negative-going excursion of the AC input signal and power supply voltage variations. The typical value is 1.2V for the 12V VCC. Biasing is not always DC; it can be AC: AC bias...