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THE MJR7-Mk5 LATERAL MOSFET CLASS-AB POWER AMPLIFIER
Tested at 4V into a 7R5 load to check for crossover effects the 1kHz distortion was mostly second harmonic under -120dB (0.0001%), achieved with only 100mA quiescent current. Power output is around 30W into 8ohms with a single 60V supply, or higher voltages can be used for up to about 100W. Two channels are included on a single 6" x 4" board.
setup and testing
photos of construction
supply effects testing
MJR7 CONSTRUCTOR'S PAGE
DESIGN THEORY - Introduction
input stage distortion
slew rate and t.i.d. also part-2
phase intermodulation distortion
capacitor distortion also part-2
output stage protection
slew rate also part-2
MJR9 FEEDFORWARD AMPLIFIER
The MJR7 circuit can easily be modified to include feedforward error reduction.
MJR11 DIRECT COUPLED MOSFET AMPLIFIER
This is one way to make the mosfet amplifier direct-coupled.
TRANSISTOR AMPLIFIER DESIGN FOR BEGINNERS. Part 1.
Part 2. Part 3. Part 4. Part 5. Part 6.
COMMON EMITTER OUTPUT IMPEDANCE.
A CLASS-B OUTPUT STAGE USING FEEDFORWARD
A simple modification to a standard class-B output stage can reduce crossover distortion and also avoid the need for accurate adjustment and thermal compensation of quiescent current.
RIAA PHONO PRE-AMP DESIGN THEORY
RIAA PHONO PRE-AMP CIRCUIT
RIAA PHONO BOARD LAYOUT
OP-AMP BASED PHONO PRE-AMP
MODIFYING THE TECHNICS SL-PG390 CD PLAYER
GUITAR PRE-AMP Mk1
GUITAR PRE-AMP Mk2
GUITAR PRE-AMP Mk3
Low distortion levels can be measured without expensive test equipment by using a signal-nulling method. The signal source distortion can also be nulled, so very low distortion signal generators are not essential.
Matching cable impedance to load impedance is sometimes advised, and here the effects of reflections from an unmatched load are investigated.
ASYMMETRIC CROSSOVER FILTERS
A LOW COST SPEAKER DESIGN
Using a full range speaker the first design tried is a 'distributed port' type.
LOW DISTORTION SIGNAL GENERATOR, Part 1
Part 2. Part 3.
THE MJR-HP2 CLASS-A HEADPHONE AMPLIFIER
This uses four field-effect transistors together with an active volume control. An output coupling capacitor is used but is included inside the feedback loop to reduce any unwanted effects. The current source for the input stage sets the dc operating level and also slows down the switch-on pulse at the output to reduce it to a harmless level. An additional jfet buffer stage can reduce distortion at high frequencies, and this is included as the HP3. Test results and layout diagram.
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