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Transistor Circuits Manual No. 4

The rapidity with which new components have appeared on the home
constructor-market in recent months has been pleasantly surprising. It
seems that,manufacturers are beginning to take new interest in this
outlet for their products.

In the field of transistors a new drift type has been made available,
the OC169. This unit has the same parameters as the OC170 but sells for
only 18/0d. which makes if far less of a luxury article. As its
characteristics are extremely good it may be used in a great many
applications that might surprise someone unfamiliar with them. Many of
,the circuits in this book make use of the OC169 and a chapter o! the
transistor itself is also included for those of you who like to know
exactly what sort of animal you are dealing with. some of it is rather
technical but a little theory does no one any harm. I have been
receiving a great many letters recently concerning the circuits that
have appeared in the transistor circuits manuals. Many of them contain
some query about one of the circuits and these I am only. too pleased
to answer although sometimes I g;; ; little behind with them. However,
I should like to hear from more of you concerning the type of equipment
you are most interested in, so perhaps you could send me a postcard.
From the letters I have received so far it appears that receivers are
the most popular projects (to borrow an excellent Americanism) and the
small pocket sets with.loudspeaker are the most popular. of all. This
has been reflected in this issue and new sets are being designed and
tested at the moment. However, there may be other types of unit which
have not yet appeared but which would be welcomed. Transistors continue
to replace valves in their traditional applications and the next take
over bid is likely to take place i,r the high fidelity field. power
transistors are now available with performances which are in no.way
inferior to those of comparable valves and these make it possible-to
design quality amplifiers, with outputs in_the region of 20 watts. As a
start in this field this manual contains the circuit for a
pre-amplifier of extremely high performance and equipment for use with
this will appear in the future manuals- whilst many still tend to think
of the transistor in terms of portable usage it, has, in fact, many
properties which make it preferable to the valve in larger types of
domestic equipment. In tape recorders and other Hi-Fi equipment, where
the elimination of mains hum is. of paramount importance, their large
scale adoption may not be far in the future.”

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