Tab Electronics Guide to Understanding Electricity ... - Sciences Club

Linear Electronic Circuits
251
all modern solid-state audio power amplifiers are designed with this
same basic three-stage architecture, commonly referred to as the Lin
three-stage topology.
Constructing the 12-Watt RMS Amplifier of
Fig. 8-8
If you decide to construct this amplifier circuit on a universal breadboard
or solderless breadboard, the construction is rather simple and
straightforward. You will need to provide some heatsinking for output
transistors Q6 and Q7. If you mount the amplifier in a small metal
enclosure, adequate heatsinking can be obtained by simply mounting
Q6 and Q7 to the enclosure (remember to ensure that Q6 and Q7 are
electrically isolated from the enclosure).
For optimum performance, diodes D1 and D3 should thermally track
the temperature of transistors Q6 and Q7. This can be accomplished in
several ways. The diodes could be glued to the case of the output devices
with a small drop of epoxy, or you can bend a small solderless “ring” terminal
into a makeshift clamp, with the ring held in place by the transistor’s
mounting bolt. If you construct the amplifier circuit similar to the
Fig. 8-9a layout, you can simply bend the diodes into a touching position
with the output transistors (remember to solder the diodes high above
the board surface if you want to use this technique).
If you plan to use a current-limited power supply to test this amplifier
circuit (such as the “lab-quality power supply” detailed in Chapters
3 through 6), fuse F1 isn’t necessary. If you provide operational power
to this amplifier circuit with a simple raw DC power supply as mentioned
earlier, F1 must be included for safety purposes. Also, keep in
mind that if you accidentally “short” (short-circuit) the speaker output
leads together, you will probably destroy one or both of the output
transistors (i.e., Q6 and Q7).
Making Printed Circuit Boards by
Hand
Making PC boards is not as difficult as you may have been led to
believe, or as your past experiences may have indicated. Circuit board