60W Linear amplifier

The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these transistors are used in inverters and smps they are easily available for around Rs: 20/-.

The IRF linear amplifier can be connected to the out put of popular VWN-QRP to get an output of 60 Watts. The circuit draws 700 ma at 60 Volt Vcc. Good heat sink is a must for the power transistor.

Alignment of the circuit is very easy. Connect a dummy load to the out put of the circuit. You can use some small bulb like 24V 6Watts as the dummy load. I have even used 230V 60Watts bulb as dummy load with my IRF840 power amplifier working at 120Volts. Adjust the 10K preset to get around 100 ma Drain current. I used gate voltage of 0.8V with my linear amplifier. A heigh gate voltage can make the power transistor get distroyed by self oscillation. So gate voltage must be below 2V and fixing at 1V will be safe.

Bifalar transformaer T1 is wound with 8 turns 26SWG on 1.4 x 1 balun core.

The coil on the drain of IRF is 3 turns 20 SWG wound on 4 number of T13.9 torroids (two torroids are stacked to form a balun core). The RFC at the Vcc line is 20 Turns 20 SWG wound on T20 torroid.

555 DC-AC Inverter

Parts List:
R1 = 10K
R2 = 100K
R3 = 100 ohm
R4 = 50K potmeter, Linear
C1,C2 = 0.1uF
C3 = 0.01uF
C4 = 2700uF
Q1 = TIP41A, NPN, or equivalent
Q2 = TIP42A, PNP, or equivalent
L1 = 1uH
T1 = Filament transformer, your choice

This DC-to-AC inverter schematic produces an AC output at line frequency and voltage. The 555 is configured as a low-frequency oscillator, tunable over the frequency range of 50 to 60 Hz by Frequency potentiometer R4.

The 555 feeds its output (amplified by Q1 and Q2) to the input of transformer T1, a reverse-connected filament transformer with the necessary step-up turns ratio. Capacitor C4 and coil L1 filter the input to T1, assuring that it is effectively a sine wave. Adjust the value of T1 to your voltage.

The output (in watts) is up to you by selecting different components.

Input voltage is anywhere from +5V to +15Volt DC, adjust the 2700uF cap's working voltage accordingly. Replacement types for Q1 are: TIP41B, TIP41C, NTE196, ECG196, etc. Replacement types for Q2 are: TIP42B, TIP42C, NTE197, ECG197, etc. Don't be afraid to use another type of similar specs, it's only a transistor... ;-)

TDA2030 typical application circuit

TDA2030 amplifier circuit to a single power law

Rated at 14 W. Power supply ± 6 ~ ± 18V. Output current, harmonic distortion and pay the small distortion (± 14V / 4 ohm, THD = 0.5%).

TDA2030 amplifier circuit to double the power law

Rated at 14 W. Power supply ± 6 ~ ± 18V. Output current, harmonic distortion and pay the small distortion (± 14V / 4 ohm, THD = 0.5%).