A handsome single chip 10 watt power amplifier can be built quite easily using the IC TDA2003 and a handful of other passive components. I had built this circuit
quite a long time ago, but I still remember the outstanding response it produced with an input music applied to it from a Sony Walkman. The circuit is very straightforward and be constructed even by a newbie.
Before learning how to build your own power amplifier, let’s first discuss the circuit functioning. The circuit description of the unit may be understood by studying the following points:
Input to the IC is received at pin #1 through capacitor C1 and the output is delivered to the loudspeaker connected to its pin #4 through a relatively large value electrolytic capacitor C4.
The IC is able to produce a fairly good response even at high frequencies, but this also means that the connected loudspeaker will be offering proportionate rising impedance to these frequencies and lowering the net efficiency of the amplifier.
An RC network consisting of R3 and C5 has been specifically introduced to rectify the above problem. It compensates for the rising frequencies and cancels out the effect of the speaker’s rising impedance.
The circuit also incorporates a feedback loop consisting of R1 and R2 that is responsible for defining the overall amplification of the unit. Here it has been set to produce an amplification of about 100 times.
Resistors R4 and capacitor C7 ensures proper stability of the IC at high frequencies by avoiding any clipping effect.
Power to the IC is applied across its pin #5 and #3. The power range is also pretty flexible and allows the amplifier to function optimally even at voltages as low as 3 volts, 18 volts being the maximum tolerable limit. Voltages above this won’t necessarily damage the IC, but the internal circuitry of the IC is so configured that in such conditions the IC will stall and just “refuse" to operate. The robust design of the IC is reinforced by internal short circuit and thermal run away protections.
The IC should be preferably fitted with a heat sink, if it’s intended to be driven continuously at its full capacity i.e. 10 watts. Again, it may be required only to avoid the IC from shutting off due to overheating, and not due to the fear of the IC getting damaged.
Please refer to the DATASHEET for the PCB layout, IC pin-outs, and other specifications.
All resistors are 1/4W CFR, 5%.
R1 = 220 Ohms,
R2 = 2.2 Ohms,
R3 = 1 Ohm,
R4 = 47 Ohms,
C1 = 10uF/10V,
C2 = 470uF/10V,
C3, C5, C7 = 100n,
C6, C4 = 1000uF/25V
IC1 = TDA 2003,
TR1 = 0-12V/1A transformer,
D1—–D4 = 1N4007
General Purpose Board,
Metallic Box, output sockets, LED indicators as per choice
The construction of this amplifier circuit is very simple and may be finished quite within an hour. Since it includes very few components, a PCB layout may not be necessary and may be easily assembled over a piece of general circuit board. Remember, the leads of the IC are fairly thick and won’t easily pass through the holes of the PCB, so better make the drillings a bit wider using a pointed screw driver before inserting it. Be careful not to break the board.
After this, it’s just a matter of soldering the IC and the associated components neatly and interconnecting their leads as per the given circuit schematic. The IC will need to be fixed somewhere at the edge of the board to facilitate easy fitting of the heat sink.
The power supply section is an ordinary transformer/bridge/capacitor type, but its placement and wiring requires some attention, which is as follows:
- Use two separate wires to connect the zero volts or the negative of the power supply to the negative of the circuit board and the loud speaker independently.
- To reduce the “hum “pickups, keep the power supply (transformer) away from the input terminal of the IC.
- Preferably use a metallic cabinet (M/S) and ground the zero terminal of the power supply to the body of the cabinet.
- Also remember to clamp the transformer to the cabinet firmly using screws/nuts and spring washers.
The testing part is simply completed with the following points:
- Initially, keep the input terminal of the IC connected to ground; connect an ammeter in series with the supply, connect a loudspeaker (with the rated value) at the output and switch ON the power.
- The meter should read about 50 mA of current which is its quiescent current drain. Also, check the DC voltage at pin #4 of the IC – it should approximately half the supply voltage.
- The above readings will confirm the proper functioning of the circuit.
- Now remove the meter and the input short circuit, and make the connections normal.
- Apply a music signal to the input of the amplifier either through your cell phone’s head phone socket or any similar source.
- The output should immediately start roaring with the amplified version of the input, optimize the volume appropriately to verify the consistency of the unit.
Well, the above procedures must have provided you with enough information regarding how to build your own power amplifier. This little music mate will keep amusing you for many many years.
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