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Semiconductors & Integrated Circuits,
High-Current Power-MOSFET Transistors
Power Regulator ICs
Switch-Mode Power Regulators /Converters ICss

Diodes / Rectifiers
Audio Power Amplifiers ICs

            Power MOSFET Switching Transistors.

High Current, small size and at a very cheap price. These transistors make perfect electronic switches for practically unlimited applications and are very easy to use.

Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) are gradually  replacing regular transistors in the industry. Very low ON-Resistance and High OFF-Resistance make them a nearest analogue of a mechanically operated switch.

MOSFET Switch can be operated by a minute electrical input signal and can be pulsed millions of times per second if necessary.

STD17NF03   ;    PHD45N03  , D-PAK   

  
 
 If the resistive load of the lamp was to be replaced by an inductive load such as a coil or solenoid, a "Flywheel" (or a Capacitive load) diode would be required in parallel with the load to protect the MOSFET from any back-emf. 
Driving an inductive load has the opposite effect from driving a capacitive load. For example, a capacitor without an electrical charge is a short circuit, resulting in a high "inrush" of current and when we remove the voltage from an inductive load we have a large reverse voltage build up as the magnetic field collapses, resulting in an induced back-emf in the windings of the inductor.

            MOSFETs -    Some useful applications examples :

Reverse polarity protection switch.

Suppose you have some sensitive electronic device which you want to protect from a Reverse current when someone inserts the batteries wrong way  (thus eliminating a possibility of damaging the circuit).

A conventional wisdom would have you insert a rectifier diode in series with the circuit. And this is good enough in most cases but the diodes have a typical voltage drop of 0.7 volt which means that instead of , say 9 volt , only 8.3 volt would reach the circuit. For many low voltage circuits this would be very undesirable voltage loss. To overcome this problem a MOSFET transistor can be used which would have a practically Zero voltage loss… Below we have a diagram for installing such protection into a guitar effect pedal as an example :

We simply break the power line and insert a MOSFET transistor. In a typical effect or any circuit with a positive power supply and a negative ground, we break the + supply line and hook up a P-channel MOSFET with its drain to the battery side and its source to the effect side, and its gate tied to ground via a 1-MegaOhm or so resistor.

Off course if you have a circuit with Positive ground and Negative supply voltage – you would use N-Channel MOSFET instead.

Timer Switch  

A momentary pressing of the S1 button deposits a charge into the C1 capacitor which keeps the MOSFET transistor Open.

 The Capacitor’s charge is slowly depleted by R1 resistor after which the transistor gradually turns off the current in the LED lamp D1.

Increased C1 and R1 values will produce longer ON time delay.

FINGER TOUCH ACTIVATED SWITCH

It does not get any easier if you want a solid state switch

that is activated by the touch of a finger.

Two small metal pins route voltage through the finger skin to a MOSFET switch.  The circuit is great for situations where a membrane type mechanical switch is not desired.

                High Current Toggle Switch with Debounced Push Button.

This circuit is useful where the load needs to be switched on from one location and switched off from another. Or simply when Push-ON-Push-OFF operation is required.

The combination (10K, 10uF and diode) on the left side of the schematic insures the circuit powers up with the load turned off. These components can be omitted if the initial power-on condition is not an issue.

When a switch is closed, the 1uF cap voltage is connected to the junction of the 220 ohm and 33K resistors causing the circuit to change state. When the switch is opened, the cap charges or discharges to the new level through the 1M resistor, and the circuit is ready to toggle again in about 1 second. It takes a little time for the cap to move to the new level, either +V or ground.

The (0.1uF) capacitor at the transistor base was added to suppress noise that might cause false triggering if the switches are located far away from the circuit.

               Power Control  - Regulator ICs

    AMS1117S-ADJ  

    3-pin SMD  800mA  Adjustable

    Low Dropout Voltage Regulator      SOT-223  SMD Package

                              Datasheet Download
    Line Regulation: 0.2% Max.

    Load Regulation: 0.4% Max.

    Operating Junction Temperature
    0 to125° C )

        Operates Down to 1V input-to-output differential

        Built-in over-Current and over-Heating Protection  (1.1A Typ.

LM317T  3-pin 1.5A, Adjustable Regulator      
TO-220 Package Datasheet Download

1.2v to 37v Adjustable range ;   40v max. Input

Built-in  Short Circuit Protection

& Current Limiting ( 2.2A typ.)

Temperature compensation

& Over-Heating Protection.

150° C Max junction temp.

Line Regulation: 0.01% typ.

Load Regulation: 0.1% typ.

LM317L  - TO-92  (Mini version)
100mA   Adjustable Regulator            Datasheet Download 

Same as above but low power version...
Guaranteed 100mA Continuous Current
(200mA Current Limiting)

Operating Junction Temperature Range -40°C  to  +125°C

LM78L08  3-pin ,  8volt  100mA  Positive Voltage Regulator ;   TO-92 package

Max. Input Voltage  30v  

Max. Power Dissipation  625mW

Dropout Voltage   1.7v

Max junction temperature 150° C

Internal Thermal Overload Protection

Internal Short-Circuit Limiting.

Higher output voltages can be achieved by introducing a resistor between pin 2 and ground…

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Pulse-Mode operation is a Power-Control technique which offers many advantages over traditional resistive methods such as : Reduced power loss , Reduced heat dissipation , Versatile Circuitry Arrangements able to function as : Step-Down Regulators , Step-Up Voltage Convertors , Voltage Invertors, etc… Pulse mode devices typically require an inductive or capacitive element as a key component in conversion process.

Pulse-mode controller ICs typically require only a few external components and are relatively easy to build.

MC34063A  8-pin DIP 1.5A Pulse-Mode
DC-to-DC Convertor / Regulator IC.                Datasheet Download

Step–Down and Step–Up and Voltage–Inverting applications with a

minimum number of external components.

Operation from 3.0 V to 40 V Input      ;      Low Standby Current

Adjustable Operation Frequency to100 kHz    ;    Built-in Current Limiting

Output Switch Current up to 1.5 A   

Adjustable Output Voltage

Precision 2% Reference

Max junction tem.150° C

    LM2576T-ADJ  SIMPLE SWITCHER 3A High-Efficiency 52kHz

    Adjustable Step-Down Voltage Regulator               Datasheet Download 

    High-efficiency replacement for popular 3-pin linear regulators.      TO-220

Logic level On-Off soft-switching.  ;  Internal frequency compensation

Thermal shutdown and current limit protection

52 kHz fixed internal oscillator

Guaranteed 3A output current

Output Voltage range 1.23v to 37v

Maximum Supply Voltage 45v

Max junction temperature 150° C

    LM2596T-ADJ  SIMPLE SWITCHER  (150 kHz)

    3A High-Efficiency Adjustable Step-Down Voltage Regulator
    150kHz version of the above.                  Datasheet Download

This Switcher is basically the same as LM2576 but with higher operational frequency and requiring smaller inductors and filter capacitors.

Both types can off course be used for all manners of Step-Up, Step-Down, Inverting and Regulating functions.   

TL494CD   2x200mA PWM Pulse-Width-Modulation Controller IC   
16-pin  DIP package             Datasheet Download

PWM is the most energy-efficient method of power control.

This Chip offers :     Complete PWM Power-Control Circuitry 

Dual Uncommitted Outputs for200-mA Sink or Source Current (250mA Max.)

Output Control Selects Single-Ended or Push-Pull Operation

Internal Circuitry Prohibits Double Pulse at Either Output

Variable Dead Time Provides Control Over Total Range
Internal Regulator Provides a Stable 5-V Reference Supply

Circuit Architecture Allows Easy Synchronization
Maximum Supply Voltage  41v

Max junction tem.150° C

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