Mosfet Circuit

Bomb Proof 150 Watt MOSFET Power Amplifier

Bomb Proof 150 Watt MOSFET Power Amplifier

In my opinion that is the best buildable high power amplifier out there. Quality of sound is just remarkable. This is a real bomb proof amplifier like the best Valve amps. Power supply circuit is also shown. Now lets see why we are going to use MOSFETS. Thermally, the MOSFET has an advantage over the bi-polar transistor. As a bi-polar transistor heats up in use, the collector current increases due to the positive temperature coefficient of the device. If the temperature rise were allowed to continue then thermal runaway would ensue and the transistor could be destroyed. A MOSFET however exhibits a negative temperature coefficient. As the device heats up in use the Drain-Source current decreases (due to increasing internal resistance), the device temperature will also reduce in turn and the Drain-Source current will then rise again.....

Mosfet 75W Power Amplifier

Mosfet 75W Power Amplifier

The MOSFETS we are dealing with are three terminal devices which are used to control electron flow in a circuit. Two of the pins (the source and drain) pass the current, and the third pin (the gate) is used to control the current. The control of current, as seen from the outside, is accomplished by placing a voltage on the gate relative to the source pin. In the case of the N- Channel MOSFET, which approximates tube operation, increased current flows from the drain through the source in response to positive gate voltage, with respect to the source voltage (fig. 2b) If you wish more current, make the gate-to- source voltage more positive (for less, make it less positive). Conduction in the N-channel MOSFET will start generally at about 4V: less than 4V, no current; more than 4V, current flows...

Automotive ignition coil

Automotive ignition coil

Here's a circuit to create a buzzcoil using a standard automotive ignition coil. A 556 dual timer is used to establish the frequency and duty cycle of the coil current. One of the timers is used as an oscillator to generate the 200 Hz rectangular waveform needed to control the (IRF740 MOSFET) while the second timer switches the oscillator on and off as the breaker points open and close (closed = on). The result is a steady stream of sparks from the ignition coil spaced about 5 milliseconds apart while the breaker points are closed. Pin 8 and 12 are the threshold and trigger inputs of one timer which are driven by the breaker points and produce an inverted signal at the timer output (pin 9). ..

MOSFET Toggle Switching circuit

MOSFET Toggle Switching circuit

This circuit was adapted from the "Toggle Switch Debounced Pushbutton" by John Lundgren. It is useful where the load needs to be switched on from one location and switched off from another. Any number of momentary (N/O) switches or push buttons can be connected in parallel. The combination (10K, 10uF and diode) on the left side of the schematic insures the circuit powers up with the load turned off and the NPN transistor conducting. These components can be omitted if the initial power-on condition is not an issue. ..

MOSFET Toggle Relay

MOSFET Toggle Relay

This circuit is similar to the one above, but uses a N channel mosfet such as IRF530, 540, 640, etc. in place of the NPN transistor. Smaller mosfets could be used, but I don't know the part numbers. I tested the circuit with a IRF640, IRFZ44, IRFZ34 and REP50N06. The circuit has the same three advantages, it requires only a few parts, always comes up with the relay deactivated, and doesn't need any switch debouncing. In operation, when the relay is deactivated, the 100uF capacitor will charge to 6 volts. ..

20 minute lamp fader

20 minute lamp fader

In this circuit, a 120VAC lamp is slowly illuminated over a approximate 20 minute period. The bridge rectifier supplies 120 DC to the MOSFET and 60 watt lamp. A 6.2K, 5 watt resistor and zener diode is used to drop the voltage to 12 volts DC for the circuit power. The bridge rectifier should be rated at 200 volts and 5 amps or more. In operation, a 700 Hz triangle waveform is generated at pin 1 of the LM324 and a slow rising voltage is obtained at pin 8. These two signals are compared at pins 12 and 13 to produce a varying duty cycle rectangular waveform at pin 14, which controls the MOSFET and brightness of the 60 watt lamp. ..

Lamp Fader schematic

Lamp Fader schematic

The sunset lamp comes on at full brightness and then slowly fades out over 1.5 hours time and stays off until power is recycled...

Touch switching 12V Light

Touch switching 12V Light

The circuit on the right uses three bipolar transistors to accomplish the same result with the touch contact referenced to the negative or ground end of the supply. Since the base of a bipolar transistor draws current and the current gain is usually less than 200, three transistors are needed to raise the microamp current level through the touch contacts to a couple amps needed by the light. For additional current, the lamp could be replaced with a 12 volt relay and diode across the coil...

Variable Fan Controller

Variable Fan Controller

When the fan seized up in my source and I changed it to a type with much less noise, turned on my computer, the largest source of noise CPU cooler fan. The computer I have a boxed Pentium III processor in slot 1, which is practically dismountable and fan replacement would be difficult. "Boxing" is a type of fan with ball bearings and replacement of the type of plain bearing to reduce noise, while cooling, but not reliability. Another option was to reduce the fan speed. I tried the program Speedfan. This enabled to set the fan speed, but I was unable to convince him to regulate the speed according to CPU temperature. ..

100W Mosfet Power Amplifier

100W Mosfet Power Amplifier

In this circuit we use the 2SK1058 and the 2SJ162 Mosfets. This could be avoided by a fairly simple bootstrapping circuit, but the improvement in maximum output may be just a fraction of a dB, depending on the supply voltage used, so too small to notice. The temperature coefficient of the output stage d.c. operating level can have a further small effect on available output, which again may be too small to be worth worrying about. Any drift will be very slow, and with capacitor coupled output this is not a problem. My own amplifier runs only slightly warm with a 60V supply, and the drift in operating point between cold and normal operating temperature gives less than a 1V variation from the optimum level for symmetric clipping...

Mosfet amplifier schematic 25 Watt

Mosfet amplifier schematic 25 Watt

Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need. Q6 & Q7 must have a small U-shaped heatsink. Q8 & Q9 must be mounted on heatsink. Adjust R11 to set quiescent current at 100mA (best measured with an Avo-meter in series with Q8 Drain) with no input signal. A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 at output ground. Then connect separately the input and output grounds at power supply ground. ..

Optical switch detector with 555

Optical switch detector with 555

When the phototransistor is stroken by IR light it conducts and the voltage between the 1Mohm resistor(arbitrary) and the phototrans drops from VCC to lower values. When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC). The amount of light that strike the phototrans necessary to bring his collector to VCC/3 is determined by the resistor (Vdrop = Icollector * R , so , if Vdrop= 2*VCC/3, the resistance needed to set the threshold on current is R=2*VCC/(Icollector*3)). ..

Logic-Driven adjustable Glow-Plug driver

Logic-Driven adjustable Glow-Plug driver

All of my turbine starts before the research on the ECU involved a very successful spark ignition. I thought (only briefly) of trying to add spark ignition to the ECU, but the mixture of delicate logic circuitry and perhaps 30,000V simply don't mix. My past experience with the hall sensor ignition for the radial engine bears this out in painful detail. So I decided to go with a glow-plug driver...

Solenoid Driver Schematic

Solenoid Driver Schematic

This same circuit was also very successfully used as a current source to supply low voltage control circuitry from the same drooper. A toroidal inductor was used with the load connected in series with ot, flywheel diode connected so that drive and flywheel current both flowed through the load. The load voltage was regulated with a zener diode. It operates by PWM - well, actually by PFM - Pulse Frequency Modulation. At power up, C1 charges up via D1 and R1. R2 will conduct, pulling the base of the emitter follower, Tr2, up and feeding gate voltage to the MOSFET. Tr4. Clearly the circuits in an analogue region during power-up, but as this is intended for use on a high voltage supply, power-up is pretty quick. ..

280 Watt MOSFET Power Amplifier

280 Watt MOSFET Power Amplifier

This amplifier is designed to be as flexible as possible, with no bad habits. Indeed, it will operate stably with supply voltages as low as +/-5V (completely pointless, but interesting), all the way to the maximum supply voltage of +/-70V. The only change that is needed is to trim the MOSFET bias pot! With the full supply voltage of +/-70V (which must not be exceeded!), RMS power is around 180W into 8 ohms, or 250W into 4ohms. Short term (or "music") power is typically about 240W into 8 ohms and 380W into 4 ohms. Note that depends to a very great degree on the power supply, and a very robust supply is an absolute requirement for the maximum output...

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