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ea BOOK CIIlOS I"lV ERT ER "0001 " '" r----~;:::::=I~~---+-- o" '" " The MC4024 device can be used also, in either crystal or capacito r ve r sions, as a vo ltage-co n trolled os c illator. In fact, it is as a vco that the device re ally earns its kee p. We need o nly apply a co ntro l Fig. 6. CMOS l "lVERTER '>o_-L_ _ -I : _ _ ~-_ '" ' Fig. 5. vo ltage to pin 2. In the case of a sweep generato r, we wo uld re place Rl a nd R2 of Fig. 3(b) with a sawtooth vo ltage. Just co nnect pin 2 to a low-impedance ou tp ut vo lt age source - see Fig. 3(d) niRUUNE"WAlTMffiR 0.45-2300 MHzj0.1-10,000watts The Standard of the Indust ry What more need we say.. , I 30303 cr I27p r • -i\;DElettroniCCorporation 194 73 Magazine· October, 1980 .... 359 Aurora Road, Cleveland (Solon) Ohio 44139 Phone: 216· 248.1200 EAST:Lanc.PA717'569-0467 WEST:Ojai,CA 805-646·7255 CMOS Circuits Those who fan cy CMO S d igita l ICs ca n make osc illato r circuits fro m ordinary gates as we ll. Also, they ma y se lect specialized IC devices from several ma nufacturers. Fig. 4(a) shows a n RC CMOS osc illator which uses a pair of NAND gates, or inverters, as the active elements. The operat ing freq ue ncy is give n roughly by F= l /l .4RC, whe re F is the frequency in Hertz, R is the resist an ce of R2 (in O hms), and C is the capacita nce of Cl in farads. Resistor Rl is used to limit the current and is given a value of Rl = (Vd d - Vss) /0 .005. If Vdd , the posit ive supply vo ltage, is + S vo lts dc and Vss is zero (i.e., grounded). then Rl will have a va lue of 1000 O hm s. A rel ated c ircuit, shown in Fig. 4(b). allows us to turn th e osc illator o n a nd off with a n external logic level. This is very handy in many digital circuit a pp lications, We do t his ne at tr ic k by replacing one of the gates with a NO R gate. O ne input is used in a manner similar to t ha t of Fig. 4(a), but t he othe r inpu t is used to ga te t he oscillator o n a nd off . A high a pplied to this term i na l turns off the oscillator , while a low turns it o n. Fig. 5 shows a variation on the circui t which ma kes it a Iittl e mo re free of frequency changes due to variat ions in power-supply vo ltages. No t all CMOS devices a re used in a we ll-regu lated power-supply environ me nt, so this c irc uit may be necessary. A CMOS crys ta l osc illator is show n in Fig. 6. T his circuit uses the common C04001 device as t he activ e element-but not ice the feedback network. It is a pi-network consisting of a c rystal (Yl) a nd two ca pacitors, Cl a nd C2. This is rela t ively stand a rd p rac t ice in CMOS circuits and is reco mmended by at least one major CMOS man ufactu rer as t he circuit of c ho ice. Feedback a nd slight fr equ ency va riat ions are possible using trimmer C2. CMOS is a slow, or lowfrequency, if you prefer, logic fam ily. It will not operate at the fre quencie s that TTL will handle easily. But, o n the othe r hand, it does ope rate nice ly at under 100 kHz ! Divide rs We do n't a lways have an oscilla tor operating on exac t ly the freq uency t ha t we need . A lt e rnatively , w e might need several frequencieswhi ch are harmonicall y rel ated . An example is the c rysta l ca librato r use d by a mate urs, CBer s, and SWLs to spot the correct frequ ency a n a communications rece ive r d ial. To provi de these, it is common practice to o pe rate the osci llator at some higher frequency (e.g., 1 MHz in t he exa m p le of the c rystal calibrator) a nd t he n d ivide down. The TTL7490 device is a nice exa mp le of a d ivide- by-l0 Ie. Its output freq ue ncy is 1/10 t he inpu t frequen cy. A casca de cha in of 7490s w ill provide a ll of the nee ded output frequencies down to a ny poi nt that yo u re quire. If division rati os ot her than 10 a re needed, then othe r ICs a re av a ila ble. In TTL, the re a re d ivide-bv-B a nd -16 devices tha t cos t peanuts. T here also are several exa m ples in CMOS, includ ing one binary counte r (C04024) and a reall y b ig d ivider (4020). If yo u reall y wa nt to get slick, the n try one of the highe r cost (and often har de r to obta in) divide-b y-N counters . These will divide by a ny ratio up to 2S6 or 1024. The exact d ivision rat io is se t by a pplyi ng a n N-b it binary wo rd to the programm ing in puts. T hese are us ua lly called p ro gra m mable d ivide-by-N counte rs.•
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Page 1 and 2:
Ii Gift to , enty Years of 73 o 174
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Rack Attack from DenTron Components
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( LEAKY LINES Dave Mann K2AGZ 3 Dan
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MEMORY KEYER BREAK THROUGHI New l
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Solid-State H.F. Kilowatt Amplifier
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Joseph D. Novak K40VK 2420 Luckett
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f MEMORY KEYER BREAKTHROUGHl The re
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73 Magazine Staff Field Strength fo
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Fig. 9. This view sho ws how the ra
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Patrick M cGuire W BSHGR 102 Dunca
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MEMORY KEYER BREAKTHROUGHI The rema
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.... Reader SelVice- see page 274 7
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un til it changed tone and wo und d
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Page 145 and 146: Two fuses are incl uded fo r safe t
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Page 149 and 150: October 1960 .. .....de W2NSD PI ,a
Page 152 and 153: A M ATEUR RADIO 73 6' YIO carRad¥
Page 154 and 155: 73 1964 January INCENTIVE LICENSING
Page 156 and 157: John W . CampbeJl W2ZCU How To Be A
Page 158 and 159: would simply melt the m selves in
Page 160 and 161: 73 1966 Oc tober de W2NSD/l de W 2N
Page 162 and 163: 162 73 Magazine . Oct ober, 1980 19
Page 164 and 165: 1969 October ...de W2NSD/l rr ay ne
Page 166 and 167: 1971 Decem ber Mean ingf ul Conu cu
Page 168 and 169: Jean Shepherd K20 RS Some Guys Make
Page 170 and 171: 1973 July .......····n~ 73's HA
Page 172 and 173: 1975 August 1: ~ '3~fr EOi TORJI'\.
Page 174 and 175: ~ ~ >. :; ....., co t" O) , f "i'
Page 176 and 177: 1978 August : :~~. Ir EOITOM'U8USHE
Page 178 and 179: 1979 March ( UJoTOM'V 8USHEII W. ..
Page 180 and 181: manage o n 4o-mete r phone for the
Page 182 and 183: Fig. 3. Basic patte rn developed fr
Page 184 and 185: of-contac t are three: New England,
Page 186 and 187: 32 ' I " 3 2 '" 3 2 ' . " 3 2 ' I "
Page 188 and 189: Gilding the Lily - FT-101 mod for c
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Page 192 and 193: Clock Blocks a compendium of TTL an
Page 196 and 197: 73 Magazine Staff Build a Better Ba
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Page 208: TUfTS Electronic Department Store,.
Page 211 and 212: t.a IO,. H r "001 ,j- ± " ~ cs r u
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Page 219 and 220: Radio Amateurs! Tempo Handh
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Page 225 and 226: ("----~) FUNl from page 28 5) The "
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