High Voltage 3 Watt Audio Power Amplifier

The LM4954 is an audio power amplifier primarily designed for demanding applications in mobile phones and other portable communication device applications. It is capable of delivering 2.4 Watts of continuous average power to an 8 BTL load with less than 1% THD+N from a 7V_DC power supply. Boomer audio power amplifiers are designed specifically to provide high quality output power with a minimal number of external components. The LM4954 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for lower-power portable applications where minimal space and power consumption are primary requirements.

High Voltage 3 Watt Audio Power Amplifier Circuit Diagram

The LM4954 features a low-power consumption global shutdown mode which is achieved by driving the shutdown pin with logic low. Additionally, the LM4954 features an internal thermal shutdown protection mechanism.

The LM4954 contains advanced pop & click circuitry which eliminates noises that would otherwise occur during turn-on and turn-off transitions.

The LM4954 is unity-gain stable and can be configured by external gain-setting resistors.

Key Specification:

Wide Power Supply Voltage Range	2.7 <= VDD <= 9V
Output Power: VDD = 7V, 1% THD+N	2.4W (typ)
Quiescent power supply current	3mA (typ)
PSRR: VDD = 5V and 3V at 217Hz	80dB (typ)
Shutdown power supply current	0.01µA (typ)

Features:

No output coupling capacitors, snubber networks or bootstrap capacitors required

Unity gain stable

Externally configurable gain

Ultra low current active low shutdown mode

BTL output can drive capacitive loads up to 100pF

"Click and pop" suppression circuitry

2.7V - 9.0V operation

Available in space-saving microSMD package

Applications

Mobile Phones

PDAs

Source: http://www.ecircuitslab.com/2011/06/high-voltage-3-watt-audio-power.html

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Voltage Controlled Oscillator

In most cases, the frequency of an oscillator is determined by the time constant RC. However, in cases or applications such as FM, tone generators, and frequency-shift keying (FSK), the frequency is to be controlled by means of an input voltage, called the control voltage. This can be achieved in a voltage-controlled oscillator (VCO). A VCO is a circuit that provides an oscillating output signal (typically of square-wave or triangular waveform) whose frequency can be adjusted over a range by a dc voltage.

Voltage Controlled Oscillator Block Diagram :

An example of a VCO is the 566 IC unit, that provides simultaneously the square-wave and triangular-wave outputs as a function of input voltage. The frequency of oscillation is set by an external resistor R1 and a capacitor C1 and the voltage Vc applied to the control terminals. Figure shows that the 566 IC unit contains current sources to charge and discharge an external capacitor Cv at a rate set by an external resistor R1 and the modulating dc input voltage.

A Schmitt trigger circuit is employed to switch the current sources between charging and discharging the capacitor, and the triangular voltage produced across the capacitor and square-wave from the Schmitt trigger are provided as outputs through buffer amplifiers. Both the output waveforms are buffered so that the output impedance of each is 50 f2. The typical magnitude of the triangular wave and the square wave are 2.4 Vpeak.to-peak and 5.4Vpeak.to.peak.

The frequency of the output waveforms is approximated by : fout = 2(V+ - Vc)/R1C1V+

Voltage Controlled Oscillator Circuit Diagram :

Figure shows the pin connection of the 566 unit. The VCO can be programmed over a 10-to-l frequency range by proper selection of an external resistor and capacitor, and then modulated over a 10-to-l frequency range by a control voltage, Vc The voltage controlled oscillators (VCOs) are commonly used in converting low-frequency signals such as EEG (electro-encephalograms) or ECG (electro-cardiograms) into an audio­frequency (AF range).

Source : http://www.ecircuitslab.com/2012/09/voltage-controlled-oscillator.html

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Low Voltage Remote Mains Switch

This circuit allows a 240V mains appliance to be controlled remotely via low-voltage cabling and a pushbutton switch. The mains appliance (in this case, a light bulb) is switched with a suitably-rated relay. All of the electronics is housed in an ABS box located in proximity to the appliance. The pushbutton switch and plugpack are located remotely and can be wired up with 3-core alarm cable or similar. Cable lengths of 20m or more are feasible with this arrangement. When the switch (S1) is pressed, the input (pin 8) of IC1c is briefly pulled low via the 10mF capacitor, which is initially discharged.

Circuit diagram:

Low-Voltage Remote Mains Switch Circuit Diagram

The output (pin 10) immediately goes high and this is inverted and fed back to the second input (pin 9) via another gate in the quad NAND package (IC1d). In conjunction with the 1MW resistor and 470nF capacitor, IC1d eliminates the effects of contact "bounce" by ensuring that IC1c’s output remains high for a predetermined period. The output from IC1c drives the clock input of a 4013 D-type flip-flop (IC2). The flipflop is wired for a "toggle" function by virtue of the Q-bar connection back to the D input. A 2.2MW resistor and 100nF capacitor improve circuit noise immunity. Each time the switch is pressed, the flipflop output (pin 13) toggles, switching the transistor (Q1) and relay on or off. Note that all mains wiring must be properly installed and completely insulated so that there is no possibility of it contacting the low-voltage side of the circuit.

 

 

http://streampowers.blogspot.com/2012/06/low-voltage-remote-mains-switch.html

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SP Network Voltage Indicator

Using this schematic is created a network voltage indicator electronic circuit. If the input voltage is gift across the network, the optocoupler transistor is open, T1 is blocked and controlled rectifier, Th1, is in a very state of conduction. Since each terminals of the piezoelectric buzzer is at identical potential, buzzer is off. If voltage disappears, the transistor T1 enters the conduction and therefore makes the terminal of buzzer to be placed on the bottom (maintains thyristor conduction state).

during this state of affairs, theres a sufficiently giant potential distinction across the buzzer and D5s to see that these 2 components to point AC power loss, each audible and visual. By pressing the reset button current is interrupted by Th1, therefore thyristor enter in blocking state and therefore the different terminal of the buzzer is connected to ground.

 

 

Source by : Streampowers

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How to Increase Current 7805 Voltage Regulator

7805 voltage regulator is one variant of the three terminal Positive Voltage Regulator. IC 7805 operated at maximum load current at a positive fixed voltage 5V 1A, but work on the maximum current will increase the thermal level. Aluminum heatsink is needed to reduce the level of heat, though internally IC 7805 has a thermal over-load protection.

The voltage regulator that works at the maximum rate is an unfavorable condition. Besides the heat level increases, it will likely be fatal if an increase in the load current due to short circuit. A good idea is to increase load current capability by adding an external transistor.

Based on the manual of IC 7805 has given a basic circuit to operate the IC at higher load currents. Download 7805 datasheet manual.

7805 Voltage Regulator Circuit 

In the following circuit to increase 7805 output current up to 3 amperes, must be added a complementary NPN transistor MJ2955. The advantage of this technique is to overcome when there is short-circuit as described above. When there is a voltage drop, then the circuit will reduce the maximum current consumption. So the problem can be solved.

7805 Voltage Regulator Circuit

Transistor BD240C in the DC voltage regulator circuit serves as a current limiting. The transistor is open when the voltage at 10R+0.22R be higher than 0.6-0.7 Volts, which leads to a reduction to zero of the T2 base current. The voltage at which the short-circuit protection starts to act, is given by voltage sum on 0.22R and 10R. Base voltage is determined by resistors 10R and 150R. In this circuit did not happen over-thermal when short-circuit occured, the maximum current was only 0.5 Ampere.

Hope this simple explanation may help in making a higher current-voltage regulator using IC 7805. You can open the manual datasheet of the 7805 voltage regulator for more information.

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