
Tncks of the trade 295
+26 to 40 V
2N3055
(0 to 25 V)
Figure
11.16 Variable supply using LM 723: 0-25 V (reproduced by courtesy of
Electronics
and
Wireless World).
of the diode then effectively connects the two
capacitors in parallel and the ripple voltage on the
raw supply will rise, but any slight hum in the
speakers is now masked by the speech or music.
Clearly the value of R should be as high as possible
without the diode conducting in the absence of
programme material, i.e. it should drop about
300 mV due to the quiescent current drawn by the
amplifier.
Amplifiers
Talking of amplifiers. Figure 11.18 shows a well-
known 'fix' for an amplifie ...