Monday, January 26, 2015
Boomer Audio Power Amplifier Using LM4906
The well-known LM386 is an excellent choice for many designs requiring a small audio power amplifier (1-watt) in a single chip. However, the LM386 requires quite a few external parts including some electrolytic capacitors, which unfortunately add volume and cost to the circuit.
National Semiconductor recently introduced its Boomer® audio integrated circuits which were designed specifically to provide high quality audio while requiring a minimum amount of external components (in surface mount packaging only). The LM4906 is capable of delivering 1 watt of continuous average power to an 8-ohm load with less than 1% distortion (THD+N) from a +5 V power supply. The chip happily works with an external PSRR (Power Supply Rejection Ratio) bypass capacitor of just 1 µF minimum.
National Semiconductor recently introduced its Boomer® audio integrated circuits which were designed specifically to provide high quality audio while requiring a minimum amount of external components (in surface mount packaging only). The LM4906 is capable of delivering 1 watt of continuous average power to an 8-ohm load with less than 1% distortion (THD+N) from a +5 V power supply. The chip happily works with an external PSRR (Power Supply Rejection Ratio) bypass capacitor of just 1 µF minimum.
In addition, no output coupling capacitors or bootstrap capacitors are required which makes the LM4906 ideally suited for cellphone and other low voltage portable applications. The LM4906 features a low-power consumption shutdown mode (the part is enabled by pulling the SD pin high).
Additionally, an internal thermal shutdown protection mechanism is provided. The LM4906 also has an internal selectable gain of either 6 dB or 12 dB. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same conditions (particularly when considering the low supply voltage of 5 to 6 volts).
Additionally, an internal thermal shutdown protection mechanism is provided. The LM4906 also has an internal selectable gain of either 6 dB or 12 dB. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same conditions (particularly when considering the low supply voltage of 5 to 6 volts).
Boomer Audio Power Amplifier Circuit Diagram:
When pushed for output power, the small SMD case has to be assisted in keeping a cool head. By adding copper foil, the thermal resistance of the application can be reduced from the free air value, resulting in higher PDMAX values without thermal shutdown protection circuitry being activated. Additional copper foil can be added to any of the leads connected to the LM4906. It is especially effective when connected to VDD, GND, and the output pins. A bridge configuration, such as the one used in LM4906, also creates a second advantage over single-ended amplifiers. Since the differential outputs, Vo1 and Vo2, are biased at half-supply, no net DC voltage exists across the load.
This eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100 Hz to 150 Hz. Thus, using a large input capacitor may not increase actual system performance. Also, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can be minimized.
Friday, December 12, 2014
Wireless IR headphone receiver schematic
6v 12vdc converter circuit
For example, you could run 12V car accessories in a 6V (British?) car.he circuit is simple, about 75% efficient and quite useful.
By changing just a few components, you can also modify it for different voltages.
Transistor Checker
This simple circuit can check transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter junctions. It can also check the output power transistors on amplifier circuits. Circuit operation is as follows. The 555 timer ( IC1 ) is set up as a 12hz multi vibrator.
The output on pin 3 drives the 4027 flip-flop ( IC2). This flip-flop divides the input frequency by two and delivers complementary voltage outputs to pin 15 and 14.
Thursday, December 11, 2014
D I Y Gold Detector Schematic
Here the very simple and easy build gold detector circuit.The circuit capable to sense gold or metal or coins from a distance of about 20cm, depending on the size of the object to detect.The circuit oscillates at ab out 140kHz and a harmonic of this frequency is detected by an AM radio.You can simply tune the radio receiver until a squeal is detected.
Thursday, November 20, 2014
Troubleshooting STR IC Regulator Power Supply
A. Unable to start.
Read More..
Can be caused by:
- No start-up voltage supply Vcc or a voltage less than 16V
- Electrolityc Capacitors supply voltage Vcc filter dry.
2. Led indicator blinking
If the supply voltage Vcc examined rocking. This is because the regulator of life and death because OVLO work., Die-protectionist regulators and auto start life over and over. If it is turned off Electrolityc Capacitors usually still keep the rest of the cargo.
Can be caused by:
- Electrolityc Capacitors supply voltage Vcc filter on a pin-4 dry. Replace with a value equal to or slightly larger. - triger UVLO
- input filter capacitor on pin-1 feed dry behind the declining value - triger OLP
- Rectifier diode of the switching transformer is damaged (sometimes when examined with avo-meter looks like a still good)
- cause the supply voltage Vcc drops of the switching transformer (UVLO)
- Part damage or broken lines on the feedback circuit of the voltage regulator through B to photocoupler - triger OVP
- Electrolityc Capacitors dry filter voltage B - triger OVP
- One of the output voltage of the switching transformer secondaries there is a short (over load) - triger OLP
- Soft start capacitor value decreases - triger OLP
3. Noise arising (noise)
Can be caused by:
- Transformer windings slack.
- If there are ceramic capacitors - can sometimes cause interference noise due to its characteristic piezoelectrik like crystal resonator. Replace with film capacitors.
4. When the st-by normal stress. But when the power is on the regulator directly off protectionism no voltage on the secondary this part. Electrolityc Capacitors are still storing charge.
Can be caused by:
- Sensor OVP small value resistor on pin-2 to the ground so that the value of delayed triger to OLP or OCP.
- Regulator IC is damaged
Excellent Electronics Heterodyne Detector
The bat ultrasounds are best up by the microphone SPKR1 and go through two stages of addition at Q1 and Q2. Separately, a tunable (R12) distinct abundance is produced by the LM567 oscillator U1. The LM567 is a accent decoder but actuality its ascribe is ashore and its voltage controlled oscillator is acclimated as a attention oscillator. The oscillator abundance is accustomed by
f = 1/(1.1*C4*(R10 + R12))
= 1/(1.1*0.0022*10-6*(4.7 + [0-50])*103)
= [88-7.5] khz
The two signals are alloyed at Q3 to aftermath both a arresting in the audio ambit and college frequencies that are again filtered out.
The actual audio arresting undergoes a aftermost date of controlled (R13) addition with the LM386 at U2 afore actuality accessible for achievement at AUDIO OUT. The ability antecedent is a simple 9V battery, so this apparatus is absolutely portable.
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