Electronic Circuit Diagram

25W Hi-Fi Audio Amplifier based LM1875 circuit diagram

Here the circuit diagram of 25 watt high fidelity audio amplifier that build based on single Power Amplifier IC LM1875.

Component part list

R1 _____________ 1K
R2 _____________ 1M
R3 _____________ 22K
R4 _____________ 10K
R5 _____________ 180K
R6 _____________ 1R

IC1 ____________ LM1875

C1 _____________ 1uF 50V
C2,6 ___________ 100nF
C3 _____________ 22uF 63V
C4 _____________ 0.22uF
C7,5 ___________ 220uF 50V     

Miscellaneous:
Fuse holder & cover
2 amp fuses

Circuit Desc:
The IC can be used with two power supply arrangements single supply and dual supply. We have decided to use the dual supply version. The single supply version would require the use of 63V electrolytic capacitors, thus increasing the cost and overall size of the module.

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2W RF Amplifier with MOSFET LF2810A circuit diagram

This is a 2W RF amplifier circuit build with power MOSFET LF2810A.

Figure A

Figure A is the schematic of the microstrip single stage RF amplifier. The amplifier is based on the M/A-Com LF2810A MOSFET. The transistor is actually a 10 watt, 28 volt part, but provides adequate gain for this application at 12 VDC. The amplifier provides greater than 40% efficiency at the desired output power. Trimmer capacitors are used for input and output matching. Output power is adjusted by a trimpot which sets the gate bias voltage.
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100W RF Amplifier with BLY94 circuit diagram

This is a 100W RF amplifier built based on RF power transistor BLY94.

Active components: BLY94
Coaxial cable length : K x Lambda / 4, where K = 0.66 for 50 ohm cable and K = 0.8 for 75 ohm cable.
L1 = L6 = 2 turns / 1.5mm / 14mm
L2 = L7 = 8turns/0.8mm/4mm/ferite or HF
L3 = L8 = 4 turns / 2mm / 14mm / gap 1mm
L4 = L9 = 20turns/0.3mm / 3mm / ferite
L5 = L10 = 1 turn / 2mm / 15mm

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Connection Tester circuit diagram

Here the low resistance connection tester which can be used as cable or wire tester, soldered joints and other types of connection with resistance value between 0.25 and 4 ohm.

Notes
This simple circuit uses a 741 op-amp in differential mode as a continuity tester. Read the rest of this entry »

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UHF TV Antenna Booster circuit diagram

This is the circuit diagram of UHF band TV antenna booster with 15dB gain power. This low cost antenna booster is simple and easy to build.

This circuit formed based on BF180 UHF Transistor. The first stage is an band pass filter constructed by the C1, CV1, L1, L4, C7 and C3, the second stage is a base-common voltage amplifier with low input impedance to match. air core coil construction and calculation here. After assembling, pack it into a proper metallic box and connect the ground of the circuit to the box to reduce noise effect.

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