Client Projects. Introduction Transistors had been invented in , resulting in the introduction of Philips semiconductor diodes in , although real production and the use in TV's only started in with the OA60 diode. The first germanium alloy transistor, the OC10, appeared the next year, but again real production was only possible with the second generation OC However, the application of semiconductors in TV's went slowly. Transistors were predominantly used in portable radios, and in all TVs up to only a handful of germanium diodes was used, mainly for audio and video detectors, supply rectifiers and an occasional switching circuit.

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Client Projects. Introduction Transistors had been invented in , resulting in the introduction of Philips semiconductor diodes in , although real production and the use in TV's only started in with the OA60 diode. The first germanium alloy transistor, the OC10, appeared the next year, but again real production was only possible with the second generation OC However, the application of semiconductors in TV's went slowly. Transistors were predominantly used in portable radios, and in all TVs up to only a handful of germanium diodes was used, mainly for audio and video detectors, supply rectifiers and an occasional switching circuit.

And then, finally, transistors were introduced in , and most surprisingly in the most difficult sub-module of the TV: the UHF tuner! It was only after this first step that the fully transistorized portable television appeared, followed by the standard TV's moving towards a hybrid transistor-valve architecture. To understand these developments we'll first have a brief look at transistors and their development in the s and s.

Once the transistor was introduced the channel selectors quickly became more compact, although the fundamental tuning mechanisms initially didn't change: drum tuners for VHF, variable capacitors for UHF. To allow finally new, all-electronic tuning yet another semiconductor element was required: the variable capacitor diode or varicap.

When these were introduced in entirely new channel selection mechanisms could be developed, with touch buttons and ultimately remote controls. In the meantime a variety of mechanical channel pre-set and selection constructions was used. Both these developments were accelerated by the third - and most important - development of TV in this period: the introduction of colour. The introduction of colour TV standards by itself had only minimal influence on the tuner design, but the explosion of functional complexity associated with colour put an enormous pressure on both size and cost reduction of all other components inside the TV, including the tuner.

This chapter will cover the period , with tuners entirely designed from transistors. In the meantime Philips continued to grow as one of the dominant players in consumer electronics, sweeping up many of its former competitors in the process.

In many cases this started with selling components the picture tube and tuner, valves and semiconductors, discrete components , followed by complete reference designs and copy production of these platforms. By that time usually only a brand name was left, when the company was acquired by Philips, often continuing the use of those brands for quite a while.

These acquisitions included companies in increasingly remote countries, like the South America, Australia and South Africa. Which in turn made for an ever wider portfolio of tuners, covering all different standards across the globe. In this decade we're therefore even going to see two Philips divisions active in developing and producing tuners: consumer electronics RGT and components Elcoma.

All in all much to discuss! In the context of this story it goes to far to dive into the fundamentals and details of the transistor, and the basics are assumed to be known, like I did for the valves in the previous period. I'll therefore focus on the specifics of the tuner application: the RF transistor. For the moment we only need to consider the "mother of all transistors", the Bipolar Junction Transistor BJT , as it was invented at Bell Labs in A summary of the early Philips diode and transistor development has been presented as part of the early television development here , and we'll continue where that story left us in The first Philips transistors, based on a patent licence from the US company RCA, were based on the so-called alloy junction concept using germanium as the base material see below picture left.

The transistor was constructed from a thin 15um thin N-doped Germanium wafer, to which on the top and bottom drops of Indium were attached through an alloying process at some degrees C. This resulted in p-type diffusion layers at the interfaces, resulting in a P-N-P structure. As can be seen from the picture, dimensions were fairly large, and these transistors could thus only be used for low frequency and audio applications. Conceptual drawing of the 2nd generation alloy diffusion germanium PNP transistor developed by Philips and Mullard, and introduced with the OC and in Production of the first generation transistors was not easy, with a lot of manual production steps, and performance accuracy was thus low.

Therefore the transistors were always "binned" in production i. Because the high frequency behaviour of a transistor is inversely proportional to the base transit time it is obvious that smaller and better controllable transistor structures were needed. This resulted in the alloy diffusion transistor, which was designed independently in two Philips labs: the Natuurkundig Laboratorium Research Lab in Eindhoven, by Jochems, Memelink and Tummers, and in the Mullard Labs by Beale.

These two groups, working on the same topic but not interacting in any practical way, show the effect of the rapidly expanding Philips organisation, as well as the by then still high independence of the national sub-brands. Both transistor concepts used a collector made from P-type Germanium as the carrier, to which a small droplet containing a mix of Gallium and Antimony was alloyed and baked at high temperature.

Because Antimony diffuses much faster in Germanium than Gallium, after a certain time at high temperature, the Antimo n y has formed an outer diffusion zone, while the Gallium forms a second and more shallow diffusion zone. Together with the P-type Germanium this resulted again in a mesa-style PNP transistor with smaller dimension and more accurately controlled base thickness. This made it useable in radio receivers, but not yet in tuners.

By this time the different branches of Philips Halfgeleiders the group Semiconductors within the HIG Elektronenbuizen Electron Valves had started local production, with historically the main factories at Nijmegen in the Netherlands and Valvo in Hamburg, Germany.

Mullard had opened a semiconductor research lab in Redhill, Surrey, in , and in started large scale production in a brand new factory in Millbrook near Southampton. All these European plants produced germanium OC-series transistors and OA-series diodes for at least a decade.

The last semiconductor fab worth mentioning here is Amperex, the US subsidiary that was acquired in , at that time mainly driven by the need for increased valve production capacity. However, in Amperex had started semiconductor manufacturing in a new fab in Hicksville, New York, which also became the headquarters of the North American Philips organization. Although the OC-transistors were to be produced for many years to come, around the end of the s a new naming convention was agreed in Europe, driven by the " Association Internationale Pro Electron ", which was implemented from With the introduction of the new European naming convention another novelty was introduced: common types.

Up until then each company had developed its own transistor variants, although in practice they might be very similar. Now, like was the case for many valves, a "standard" performance was defined for a common type transistor, which could then be produced by multiple companies.

However, since the common specs could be rather widely defined, in practice companies created dedicated sub-types within the common spec envelope, e. UHF had to wait for the AF, a MHz transistor, although also here the highest operational frequency was very close to the fT, with the associated performance degradation at the upper end of the band. The AF was developed by Siemens on the request of the Grundig tuner group, and it seems that Philips initially used the Siemens transistors.

In contrast to the valve triode, which has an almost infinite input impedance and the basic amplification is input grid voltage to output anode current, the bipolar transistor is a current-to-current amplifier. In other words, there is a measurable input base current.

For DC behaviour all capacitances can be neglected. The high-frequency characteristics are mainly determined by the base-emitter capacitance Cb, which is proportional to the forward base transit time, and the collector-base depletion capacitance of the reverse biased collector-base junction Cu. In other words, the amplification reduces with increasing frequency.

The frequency where the current gain has reduced to 1 is called the transition frequency fT, the main defining parameter of RF transistors. The other non-ideal elements of the transistor equivalent model do not directly influence the fT, but do have an effect on other RF parameters: - the base series resistance rB degrades the Noise Figure - the emitter series resistance rE induces voltage feedback, reducing the gain - the collector output capacitance cCE limits the output bandwidth All these elements, including the fT, in principle reduce with a shrinking size of the transistor.

The 1st generation OC transistors were encapsulated in glass, which received a black paint or metal cover. The AF, here with gold plated leads. The AF, which introduced the standardized TO-5 metal housing. AF, introducing the smaller TO72 housing. TO72 dimensions. This remained the standard small metal package until plastic was introduced.

The pressure on the development groups of transistor tuners was obvious: provide smaller, and thus material-wise much cheaper tuners with a performance at least equal to that of the then optimal valve tuners.

I'm sure that an integral cost that was almost equal to the valve tuner was acceptable for the first generation, price erosion would come with volume. Simple as it may sound, this was no easy task!

And although the noise performance of the PCPC86 combination at especially the upper UHF band edge was not spectacular, the performance of transistors on this parameter was not better at all!

The very first effort at a transistorized UHF tuner was literally a valve tuner in which the triodes had been replaced by AF transistors; if we compare the AT schematic diagram on the right the resemblance with the AT is remarkable. The conceptual set-up was therefore also identical: a first common base RF pre-amplifier followed by a double tuned BPF, and finally a self-oscillating common base MO. All this using three tuned sections as in the valve tuner.

Even the mechanical design was very similar, with the two metal cans of the transistors protruding through the can top. It is likely that performance of this very first tuner was still mediocre, since it was initially only used very briefly in just two German TV sets, the 23TD and These were the German versions of the 23TXA with the advanced motor controlled tuning system. In a slightly optimized version using the new AF transistor was used in Eindhoven in the TV platforms.

The components shaded red were to be changed or deleted in the next generation AT Very quickly the AT was superseded, however, by the AT, essentially an optimization. The main drawback of the has probably been bad noise performance at the higher portions of the UHF band. This can only be countered by tuning out this capacitor with an inductance, and this exactly what we see in the AT a fourth tuned filter in the form of a input BPF, similar to the typical VHF input.

So the changes were: using 4 instead of 3 tuned filter segments so now input, double tuned BPF, oscillator tank circuit reduction of the number of capacitive alignment trimmers red in the AT circuit diagram relocation of the transistors from the top of the box to the centre the internal gear was deleted and the control axis moved to the other side of the box near the RF input. This was to facilitate more direct control of push button pre-set assemblies that will be discussed later smaller height of the module.

These changes are highlighted in below picture showing both the AT and Red are components deleted from the AT, green the new input tunable section. Blue shows the change of location of the transistors. The latter was the first to introduce the new generation Ge alloy diffusion transistor AF, which was especially promoted by Mullard.

Most likely through a size reduction the AF was the first to have an fT well above MHz; the minimal spec for the common type AF was MHz, but data sheets suggest selected transistors could reach MHz. But quickly a cost reduction was introduced in the form of the AT, which had most DC resistors moved out of the box to a small PCB on top of it, thus reducing the amount of difficult component mounting inside the small chambers of the UHF module.

Especially in France many versions of this tuner were used. In two final upgrades were introduced: the Eindhoven organization launched the AT, using the latest AF transistor for the RF input stage. Interior view of the AT, clearly showing the 4 tuning capacitors and the reduced interior component count. Backside of the AT, showing the one piece moulded "bathtub" concept. A further cost reduction was the plastic front cover.

For shielding a copper foil was mounted on the inside. Production code PT indicates it was produced in Portugal in , probably week or batch The blue section indicates the PCB and the externally mounted components.

Also based on the new transistor UHF module a converter box was designed, as successor of the valve-based NT The UVC2, as the module was called, thus used a three-section tuner, although it introduced the AF transistors. The tuner contained the internal gear, so tuning was done using a big thumb wheel.


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