| www/Articles/_TEXTS_KROUZEK/03_Proudove zrcadlo/HTML/p.htm | ||
|---|---|---|
| 1 |
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
|
| 2 |
<html> |
|
| 3 |
<head> |
|
| 4 |
<meta http-equiv="Content-Type" content="text/html; charset=windows-1250" |
|
| 5 |
<title> |
|
| 6 |
proudov? zrcadlo |
|
| 7 |
</title> |
|
| 8 |
<link rel="StyleSheet" href="../../../../Web/CSS/MLAB.css" type="text/css" title="MLAB z?kladn? styl"> |
|
| 9 |
<script language="JavaScript" type="text/javascript" src="../../../../Web/JS/MLAB_Menu.js"></script> |
|
| 10 |
</head> |
|
| 11 |
|
|
| 12 |
<body lang="cs"> |
|
| 13 |
|
|
| 14 |
<!-- ============== HLAVI?KA ============== --> |
|
| 15 |
<div class="Header"> |
|
| 16 |
<script type="text/javascript"> |
|
| 17 |
<!-- |
|
| 18 |
SetRelativePath("../../../../");
|
|
| 19 |
DrawHeader(); // mozno zmenit nadpis v hlavicce |
|
| 20 |
// --> |
|
| 21 |
</script> |
|
| 22 |
<noscript> |
|
| 23 |
<b> Pro zobrazen? (vlo?en?) hlavi?ky je pot?eba JavaScript </b> |
|
| 24 |
</noscript> |
|
| 25 |
</div> |
|
| 26 |
|
|
| 27 |
<!-- ============== MENU ============== --> |
|
| 28 |
<div class="Menu"> |
|
| 29 |
<script type="text/javascript"> |
|
| 30 |
<!-- |
|
| 31 |
|
|
| 32 |
DrawMenu(); |
|
| 33 |
// --> |
|
| 34 |
</script> |
|
| 35 |
<noscript> |
|
| 36 |
<b> Pro zobrazen? (vlo?en?) hlavi?ky je pot?eba JavaScript </b> |
|
| 37 |
</noscript> |
|
| 38 |
</div> |
|
| 39 |
|
|
| 40 |
<!-- ============== TEXT STRANKY ============== --> |
|
| 41 |
<div class="Text"> |
|
| 42 |
<p class="Titul"> |
|
| 43 |
Proudov? zrcadlo |
|
| 44 |
</p> |
|
| 45 |
<p class="Autor"> |
|
| 46 |
Milan Horkel |
|
| 47 |
</p> |
|
| 48 |
<p class="Subtitle"> |
|
| 49 |
Zdroje proudu jsou p?i konstrukci integrovan?ch obvod? asi stejn? d?le?it?, jako oby?ejn? |
|
| 50 |
rezistor pro b??n? tranzistorov? obvody. Zdroje proudu se ?asto pou??vaj? m?sto |
|
| 51 |
zat??ovac?ch odpor? v? kolektorech zesilovac?ch stup?? a v? diferenci?ln?ch stupn?ch |
|
| 52 |
(opera?n?ch) zesilova??. |
|
| 53 |
</p> |
|
| 54 |
<h1> |
|
| 55 |
1.Jednoduch? zdroj proudu |
|
| 56 |
</h1> |
|
| 57 |
<p> |
|
| 58 |
<img width="242" height="255" src="pic/image001.gif" alt="Image"> <img width="234" height= |
|
| 59 |
"255" src="pic/image002.gif" alt="Image"> |
|
| 60 |
</p> |
|
| 61 |
<p> |
|
| 62 |
Tento zdroj proudu funguje tak, ?e se nap?t? na Zenerov? diod? zesiluje emitorov?m |
|
| 63 |
sledova?em (zesilova?em se spole?n?m kolektorem) tak, ?e na odporu Re je nap?t? Uz zmen?en? |
|
| 64 |
o ?bytek na p?echodu B-E (cca 0.7V).? Pokud toto nap?t? klesne, pote?e v?t?? proud |
|
| 65 |
p?echodem B-E a tranzistor se bude otev?rat a bude tak do Re propou?t?t v?t?? proud a |
|
| 66 |
naopak. |
|
| 67 |
</p> |
|
| 68 |
<p> |
|
| 69 |
Proto?e proud kolektorem je prakticky stejn? jako proud emitorem (je men?? o proud b?ze, |
|
| 70 |
kter? je beta kr?t men??) bude se tranzistor otev?rat a zav?rat tak, aby proud z?t??? byl |
|
| 71 |
st?le stejn?. |
|
| 72 |
</p> |
|
| 73 |
<p> |
|
| 74 |
Toto sch?ma ukazuje konkr?tn? pou?it? zdroje proudu pro nab?je?ku NiCd akumul?tor? v? |
|
| 75 |
re?imu konstantn?ho proudu. |
|
| 76 |
</p> |
|
| 77 |
<p> |
|
| 78 |
Zdroj proudu m??e fungovat pouze v? p??pad?, ?e je nap?jec? dostate?n? velk? na to, aby p?i |
|
| 79 |
nastaven?m proudu zbylo je?t? n?jak? nap?t? i na tranzistor. |
|
| 80 |
</p> |
|
| 81 |
<p> |
|
| 82 |
Velikost nap?jec?ho nap?t? je omezeno maxim?ln?m nap?t?m, kter? tranzistor snese a |
|
| 83 |
maxim?ln?m v?konem, kter? je mo?n? na tranzistoru uchladit. |
|
| 84 |
</p> |
|
| 85 |
<p> |
|
| 86 |
<img width="359" height="166" src="pic/image003.gif" alt="Image"> |
|
| 87 |
</p> |
|
| 88 |
<p> |
|
| 89 |
To je princip?ln? stejn? zdroj proudu. Obvod LM317 se sna?? udr?ovat mezi v?vody OUT a ADJ |
|
| 90 |
konstantn? nap?t? 1.25V. T?m je d?n proud rezistorem Re a t?m i z?t???. P?esnost je zde |
|
| 91 |
pon?kud zhor?ena proudem Iq ze vstupu ADJ stabiliz?toru. |
|
| 92 |
</p> |
|
| 93 |
<h1> |
|
| 94 |
2. Tranzistor jako dioda |
|
| 95 |
</h1> |
|
| 96 |
<p> |
|
| 97 |
<img width="107" height="255" src="pic/image004.gif" alt="Image"> |
|
| 98 |
</p> |
|
| 99 |
<p> |
|
| 100 |
U tranzistoru zapojen?ho podle obr?zku se proud proch?zej?c? rezistorem P rozd?l? na proud |
|
| 101 |
b?ze a proud kolektoru podle proudov?ho zesilovac?ho ?initele tranzistoru: |
|
| 102 |
</p> |
|
| 103 |
<p> |
|
| 104 |
<img width="73" height="19" src="pic/image005.gif" alt="Image"> |
|
| 105 |
</p> |
|
| 106 |
<p> |
|
| 107 |
Tranzistor se bude otev?rat do t? doby, a? bude nap?t? na b?zi (a kolektoru) zmen?? na cca |
|
| 108 |
0.7V. |
|
| 109 |
</p> |
|
| 110 |
<p> |
|
| 111 |
Takto zapojen? tranzistor se b??n? objevuje v? integrovan?ch obvodech v? m?stech, kde je |
|
| 112 |
pot?eba posunout nap?t? o cca 0.7V. |
|
| 113 |
</p> |
|
| 114 |
<h1> |
|
| 115 |
3. Proudov? zrcadlo |
|
| 116 |
</h1> |
|
| 117 |
<p> |
|
| 118 |
<img width="193" height="215" src="pic/image006.gif" alt="Image"> |
|
| 119 |
</p> |
|
| 120 |
<p> |
|
| 121 |
Uveden? zapojen? se jmenuje proudov? zrcadlo, proto?e nastaven? proud Iref na vstupu ur?uje |
|
| 122 |
proud z?t??? Iz. Pokud jsou oba tranzistory stejn? a maj? stejnou teplotu bude: |
|
| 123 |
</p> |
|
| 124 |
<p> |
|
| 125 |
<img width="48" height="19" src="pic/image007.gif" alt="Image"> |
|
| 126 |
</p> |
|
| 127 |
<p> |
|
| 128 |
Prvn? tranzistor funguje jako dioda a pokud jsou oba tranzistory stejn? a maj? stejnou |
|
| 129 |
teplotu pote?e do b?ze druh?ho tranzistoru stejn? proud jako do prvn?ho tranzistoru. |
|
| 130 |
</p> |
|
| 131 |
<p> |
|
| 132 |
<img width="51" height="19" src="pic/image008.gif" alt="Image"> |
|
| 133 |
</p> |
|
| 134 |
<p> |
|
| 135 |
T?m je druh? tranzistor otev?en? pro stejn? proud jako tranzistor prvn?. |
|
| 136 |
</p> |
|
| 137 |
<p> |
|
| 138 |
<img width="199" height="250" src="pic/image009.gif" alt="Image"> |
|
| 139 |
</p> |
|
| 140 |
<p> |
|
| 141 |
Toto je stejn? zapojen? ale s? konkr?tn?mi proudy a nap?t?mi. Je vid?t, ?e p?evodn? pom?r |
|
| 142 |
zrcadla nen? p?esn? 1:1 ale ??st referen?n?ho proudu se spot?ebuje pro nap?jen? b?z? obou |
|
| 143 |
tranzistor?. P?esnost je t?m lep??, ??m je v?t?? zes?len? obou tranzistor?. |
|
| 144 |
</p> |
|
| 145 |
<p> |
|
| 146 |
U integrovan?ch obvod? je obt??n? dos?hnout konkr?tn? velikosti zes?len, ale je snadn? |
|
| 147 |
vyrobit tranzistory, kter? jsou stejn?. |
|
| 148 |
</p> |
|
| 149 |
<p> |
|
| 150 |
<img width="244" height="250" src="pic/image010.gif" alt="Image"> |
|
| 151 |
</p> |
|
| 152 |
<p> |
|
| 153 |
Pokud vezmeme dva oby?ejn? tranzistory bude p?evodn? pom?r zrcadla ur?it? jin? ne? 1:1 ale |
|
| 154 |
zrcadlo bude p?kn? fungovat. V??n?m probl?mem ale bude udr?en? shodn? teploty obou |
|
| 155 |
tranzistor?. Proto?e na teplot? z?vis? nap?t? Ube (vy??? teplota znamen? ni??? nap?t? na |
|
| 156 |
diod? Ube) bude se p?evodn? pom?r zrcadla m?nit s? rozd?lem teploty obou tranzistor?. |
|
| 157 |
</p> |
|
| 158 |
<p> |
|
| 159 |
Zrcadlo m??e zrcadlit referen?n? proud do v?t??ho po?tu v?stup?. Tranzistor Q2 nen? nijak |
|
| 160 |
zvl??tn?, to se jen kresl? b?ze jako by byla pr?choz? aby bylo sch?ma p?ehledn?j??. |
|
| 161 |
</p> |
|
| 162 |
<p> |
|
| 163 |
Pokud konstrukt?r integrovan?ho obvodu pot?ebuje jin? p?evodn? pom?r ne? 1:1 tak ud?l? |
|
| 164 |
n?kter? v?stupn? tranzistoru v?t?? a n?kter? men??. |
|
| 165 |
</p> |
|
| 166 |
<p> |
|
| 167 |
V?t?? tranzistor si m??eme p?edstavit jako n?kolik mal?ch tranzistor? spojen?ch paraleln?. |
|
| 168 |
Tedy i v?stupn? proud bude v?t??. |
|
| 169 |
</p> |
|
| 170 |
<p> |
|
| 171 |
<img width="212" height="250" src="pic/image011.gif" alt="Image"> |
|
| 172 |
</p> |
|
| 173 |
<p> |
|
| 174 |
Posledn? zapojen? ukazuje, jak zlep?it p?esnost zrcadlen? referen?n?ho proudu. Tranzistor |
|
| 175 |
Q3 funguje jako emitorov? sledova? a nap?j? b?ze Q1 a Q2 ani? by podstatn? u??ral |
|
| 176 |
referen?n? proud. |
|
| 177 |
</p> |
|
| 178 |
<p> |
|
| 179 |
Nap?t? na kolektoru Q1 bude cca 2x0.7V. |
|
| 180 |
</p> |
|
| 181 |
<h1> |
|
| 182 |
4. Kde se proudov? zrcadlo pou??v? |
|
| 183 |
</h1> |
|
| 184 |
<p> |
|
| 185 |
Stru?n? ?e?eno, proudov? zrcadlo se pou??v? ve v?ech analogov?ch integrovan?ch obvodech i |
|
| 186 |
v? mnoh?ch ??slicov?ch integrovan?ch obvodech. Pou?it? proudov?ho zrcadla a zdroje proudu |
|
| 187 |
jako z?t??e pro tranzistory, kter? zesiluj? u?ite?n? sign?l p?in??? obrovsk? v?hody: |
|
| 188 |
</p> |
|
| 189 |
<ul type="disc"> |
|
| 190 |
<li>Zesilova?e zesiluj? nez?visle na velikosti nap?jec?ho nap?t? |
|
| 191 |
</li> |
|
| 192 |
<li>Zesilova?e mohou zesilovat velk? sign?ly bez zkreslen? |
|
| 193 |
</li> |
|
| 194 |
<li>Rozkmit sign?l? m??e b?t t?m?? p?es cel? rozsah nap?jen? |
|
| 195 |
</li> |
|
| 196 |
<li>Obvod se obejde bez rezistor?, kter? zab?raj? velkou plochu na ?ipu |
|
| 197 |
</li> |
|
| 198 |
</ul> |
|
| 199 |
<p> |
|
| 200 |
Pod?v?me se na zapojen? jednoduch?ho kompar?toru LM339. Kompar?tor je obvod, kter? na sv?m |
|
| 201 |
v?stupu indikuje polaritu nap?t? mezi sv?mi vstupy. Velk?mu nap?t? na + vstupu odpov?d? |
|
| 202 |
velk? nap?t? na v?stupu. P?esn?ji, pokud je nap?t? na + vstupu v?t?? ne? na ? vstupu je na |
|
| 203 |
v?stupu velk? nap?t? (rozpojen? v?stupn? tranzistor) a naopak. |
|
| 204 |
</p> |
|
| 205 |
<p> |
|
| 206 |
<img width="325" height="219" src="pic/image012.jpg" alt="Image"> |
|
| 207 |
<img width="367" height="333" src="pic/image013.jpg" alt="Image"> |
|
| 208 |
</p> |
|
| 209 |
<p> |
|
| 210 |
Obvod Q13, R1, D5, D6 tvo?? jednoduch? proudov? zdroj. Proud ur?uje R1 na kter?m bude cca |
|
| 211 |
0.7V. |
|
| 212 |
</p> |
|
| 213 |
<p> |
|
| 214 |
Odpor R2 je startovac?. Bez n?ho by po zapnut? nap?jen? IO neza?al fungovat proto?e by |
|
| 215 |
v?echny tranzistory z?staly zav?en?. |
|
| 216 |
</p> |
|
| 217 |
<p> |
|
| 218 |
Tranzistory Q9, Q12, Q14 tvo?? proudov? zrcadlo a nap?j? p??slu?n? ??sti obvodu. |
|
| 219 |
</p> |
|
| 220 |
<p> |
|
| 221 |
Tranzistory Q5, Q6 jsou tak? proudov? zrcadlo a slou?? jako zat??ovac? odpory vstupn?m |
|
| 222 |
tranzistor?m Q2, Q4, kter? jsou zapojen? jako rozd?lov? zesilova?. |
|
| 223 |
</p> |
|
| 224 |
<p> |
|
| 225 |
Druh? obvod je to sam? ale z? katalogu jin?ho v?robce. ?asto se pomocn? obvody v? |
|
| 226 |
integrovan?ch obvodech kresl? zjednodu?en? nebo se nekresl? v?bec (nap??klad r?zn? ochrann? |
|
| 227 |
obvody). |
|
| 228 |
</p> |
|
| 229 |
<p> |
|
| 230 |
Proudov? zdroje r?zn? v?robci kresl? r?zn?. Tady jsou n?kter? z? b??n?ch mo?nost?: |
|
| 231 |
</p> |
|
| 232 |
<p> |
|
| 233 |
<img width="64" height="41" src="pic/image014.jpg" alt="Image"> |
|
| 234 |
<img width="68" height="40" src="pic/image015.jpg" alt="Image"> |
|
| 235 |
<img width="44" height="40" src="pic/image016.jpg" alt="Image"> |
|
| 236 |
<img width="29" height="41" src="pic/image017.jpg" alt="Image"> |
|
| 237 |
</p> |
|
| 238 |
</div> |
|
| 239 |
|
|
| 240 |
<!-- ============== PATICKA ============== --> |
|
| 241 |
<div class=Footer> |
|
| 242 |
<script type="text/javascript"> |
|
| 243 |
<!-- |
|
| 244 |
DrawFooter(); |
|
| 245 |
// --> |
|
| 246 |
</script> |
|
| 247 |
<noscript> |
|
| 248 |
<b> Pro zobrazen? (vlo?en?) hlavi?ky je pot?eba JavaScript </b> |
|
| 249 |
</noscript> |
|
| 250 |
</div> |
|
| 251 |
|
|
| 252 |
</body> |
|
| 253 |
|
|
| 254 |
</html> |
|
| Articles/_TEXTS_KROUZEK/03_Proudove zrcadlo/HTML/p.htm | ||
|---|---|---|
| 1 |
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
|
| 2 |
<html> |
|
| 3 |
<head> |
|
| 4 |
<meta http-equiv="Content-Type" content="text/html; charset=windows-1250" |
|
| 5 |
<title> |
|
| 6 |
proudov? zrcadlo |
|
| 7 |
</title> |
|
| 8 |
<link rel="StyleSheet" href="../../../../Web/CSS/MLAB.css" type="text/css" title="MLAB z?kladn? styl"> |
|
| 9 |
<script language="JavaScript" type="text/javascript" src="../../../../Web/JS/MLAB_Menu.js"></script> |
|
| 10 |
</head> |
|
| 11 |
|
|
| 12 |
<body lang="cs"> |
|
| 13 |
|
|
| 14 |
<!-- ============== HLAVI?KA ============== --> |
|
| 15 |
<div class="Header"> |
|
| 16 |
<script type="text/javascript"> |
|
| 17 |
<!-- |
|
| 18 |
SetRelativePath("../../../../");
|
|
| 19 |
DrawHeader(); // mozno zmenit nadpis v hlavicce |
|
| 20 |
// --> |
|
| 21 |
</script> |
|
| 22 |
<noscript> |
|
| 23 |
<b> Pro zobrazen? (vlo?en?) hlavi?ky je pot?eba JavaScript </b> |
|
| 24 |
</noscript> |
|
| 25 |
</div> |
|
| 26 |
|
|
| 27 |
<!-- ============== MENU ============== --> |
|
| 28 |
<div class="Menu"> |
|
| 29 |
<script type="text/javascript"> |
|
| 30 |
<!-- |
|
| 31 |
|
|
| 32 |
DrawMenu(); |
|
| 33 |
// --> |
|
| 34 |
</script> |
|
| 35 |
<noscript> |
|
| 36 |
<b> Pro zobrazen? (vlo?en?) hlavi?ky je pot?eba JavaScript </b> |
|
| 37 |
</noscript> |
|
| 38 |
</div> |
|
| 39 |
|
|
| 40 |
<!-- ============== TEXT STRANKY ============== --> |
|
| 41 |
<div class="Text"> |
|
| 42 |
<p class="Titul"> |
|
| 43 |
Proudov? zrcadlo |
|
| 44 |
</p> |
|
| 45 |
<p class="Autor"> |
|
| 46 |
Milan Horkel |
|
| 47 |
</p> |
|
| 48 |
<p class="Subtitle"> |
|
| 49 |
Zdroje proudu jsou p?i konstrukci integrovan?ch obvod? asi stejn? d?le?it?, jako oby?ejn? |
|
| 50 |
rezistor pro b??n? tranzistorov? obvody. Zdroje proudu se ?asto pou??vaj? m?sto |
|
| 51 |
zat??ovac?ch odpor? v? kolektorech zesilovac?ch stup?? a v? diferenci?ln?ch stupn?ch |
|
| 52 |
(opera?n?ch) zesilova??. |
|
| 53 |
</p> |
|
| 54 |
<h1> |
|
| 55 |
1.Jednoduch? zdroj proudu |
|
| 56 |
</h1> |
|
| 57 |
<p> |
|
| 58 |
<img width="242" height="255" src="pic/image001.gif" alt="Image"> <img width="234" height= |
|
| 59 |
"255" src="pic/image002.gif" alt="Image"> |
|
| 60 |
</p> |
|
| 61 |
<p> |
|
| 62 |
Tento zdroj proudu funguje tak, ?e se nap?t? na Zenerov? diod? zesiluje emitorov?m |
|
| 63 |
sledova?em (zesilova?em se spole?n?m kolektorem) tak, ?e na odporu Re je nap?t? Uz zmen?en? |
|
| 64 |
o ?bytek na p?echodu B-E (cca 0.7V).? Pokud toto nap?t? klesne, pote?e v?t?? proud |
|
| 65 |
p?echodem B-E a tranzistor se bude otev?rat a bude tak do Re propou?t?t v?t?? proud a |
|
| 66 |
naopak. |
|
| 67 |
</p> |
|
| 68 |
<p> |
|
| 69 |
Proto?e proud kolektorem je prakticky stejn? jako proud emitorem (je men?? o proud b?ze, |
|
| 70 |
kter? je beta kr?t men??) bude se tranzistor otev?rat a zav?rat tak, aby proud z?t??? byl |
|
| 71 |
st?le stejn?. |
|
| 72 |
</p> |
|
| 73 |
<p> |
|
| 74 |
Toto sch?ma ukazuje konkr?tn? pou?it? zdroje proudu pro nab?je?ku NiCd akumul?tor? v? |
|
| 75 |
re?imu konstantn?ho proudu. |
|
| 76 |
</p> |
|
| 77 |
<p> |
|
| 78 |
Zdroj proudu m??e fungovat pouze v? p??pad?, ?e je nap?jec? dostate?n? velk? na to, aby p?i |
|
| 79 |
nastaven?m proudu zbylo je?t? n?jak? nap?t? i na tranzistor. |
|
| 80 |
</p> |
|
| 81 |
<p> |
|
| 82 |
Velikost nap?jec?ho nap?t? je omezeno maxim?ln?m nap?t?m, kter? tranzistor snese a |
|
| 83 |
maxim?ln?m v?konem, kter? je mo?n? na tranzistoru uchladit. |
|
| 84 |
</p> |
|
| 85 |
<p> |
|
| 86 |
<img width="359" height="166" src="pic/image003.gif" alt="Image"> |
|
| 87 |
</p> |
|
| 88 |
<p> |
|
| 89 |
To je princip?ln? stejn? zdroj proudu. Obvod LM317 se sna?? udr?ovat mezi v?vody OUT a ADJ |
|
| 90 |
konstantn? nap?t? 1.25V. T?m je d?n proud rezistorem Re a t?m i z?t???. P?esnost je zde |
|
| 91 |
pon?kud zhor?ena proudem Iq ze vstupu ADJ stabiliz?toru. |
|
| 92 |
</p> |
|
| 93 |
<h1> |
|
| 94 |
2. Tranzistor jako dioda |
|
| 95 |
</h1> |
|
| 96 |
<p> |
|
| 97 |
<img width="107" height="255" src="pic/image004.gif" alt="Image"> |
|
| 98 |
</p> |
|
| 99 |
<p> |
|
| 100 |
U tranzistoru zapojen?ho podle obr?zku se proud proch?zej?c? rezistorem P rozd?l? na proud |
|
| 101 |
b?ze a proud kolektoru podle proudov?ho zesilovac?ho ?initele tranzistoru: |
|
| 102 |
</p> |
|
| 103 |
<p> |
|
| 104 |
<img width="73" height="19" src="pic/image005.gif" alt="Image"> |
|
| 105 |
</p> |
|
| 106 |
<p> |
|
| 107 |
Tranzistor se bude otev?rat do t? doby, a? bude nap?t? na b?zi (a kolektoru) zmen?? na cca |
|
| 108 |
0.7V. |
|
| 109 |
</p> |
|
| 110 |
<p> |
|
| 111 |
Takto zapojen? tranzistor se b??n? objevuje v? integrovan?ch obvodech v? m?stech, kde je |
|
| 112 |
pot?eba posunout nap?t? o cca 0.7V. |
|
| 113 |
</p> |
|
| 114 |
<h1> |
|
| 115 |
3. Proudov? zrcadlo |
|
| 116 |
</h1> |
|
| 117 |
<p> |
|
| 118 |
<img width="193" height="215" src="pic/image006.gif" alt="Image"> |
|
| 119 |
</p> |
|
| 120 |
<p> |
|
| 121 |
Uveden? zapojen? se jmenuje proudov? zrcadlo, proto?e nastaven? proud Iref na vstupu ur?uje |
|
| 122 |
proud z?t??? Iz. Pokud jsou oba tranzistory stejn? a maj? stejnou teplotu bude: |
|
| 123 |
</p> |
|
| 124 |
<p> |
|
| 125 |
<img width="48" height="19" src="pic/image007.gif" alt="Image"> |
|
| 126 |
</p> |
|
| 127 |
<p> |
|
| 128 |
Prvn? tranzistor funguje jako dioda a pokud jsou oba tranzistory stejn? a maj? stejnou |
|
| 129 |
teplotu pote?e do b?ze druh?ho tranzistoru stejn? proud jako do prvn?ho tranzistoru. |
|
| 130 |
</p> |
|
| 131 |
<p> |
|
| 132 |
<img width="51" height="19" src="pic/image008.gif" alt="Image"> |
|
| 133 |
</p> |
|
| 134 |
<p> |
|
| 135 |
T?m je druh? tranzistor otev?en? pro stejn? proud jako tranzistor prvn?. |
|
| 136 |
</p> |
|
| 137 |
<p> |
|
| 138 |
<img width="199" height="250" src="pic/image009.gif" alt="Image"> |
|
| 139 |
</p> |
|
| 140 |
<p> |
|
| 141 |
Toto je stejn? zapojen? ale s? konkr?tn?mi proudy a nap?t?mi. Je vid?t, ?e p?evodn? pom?r |
|
| 142 |
zrcadla nen? p?esn? 1:1 ale ??st referen?n?ho proudu se spot?ebuje pro nap?jen? b?z? obou |
|
| 143 |
tranzistor?. P?esnost je t?m lep??, ??m je v?t?? zes?len? obou tranzistor?. |
|
| 144 |
</p> |
|
| 145 |
<p> |
|
| 146 |
U integrovan?ch obvod? je obt??n? dos?hnout konkr?tn? velikosti zes?len, ale je snadn? |
|
| 147 |
vyrobit tranzistory, kter? jsou stejn?. |
|
| 148 |
</p> |
|
| 149 |
<p> |
|
| 150 |
<img width="244" height="250" src="pic/image010.gif" alt="Image"> |
|
| 151 |
</p> |
|
| 152 |
<p> |
|
| 153 |
Pokud vezmeme dva oby?ejn? tranzistory bude p?evodn? pom?r zrcadla ur?it? jin? ne? 1:1 ale |
|
| 154 |
zrcadlo bude p?kn? fungovat. V??n?m probl?mem ale bude udr?en? shodn? teploty obou |
|
| 155 |
tranzistor?. Proto?e na teplot? z?vis? nap?t? Ube (vy??? teplota znamen? ni??? nap?t? na |
|
| 156 |
diod? Ube) bude se p?evodn? pom?r zrcadla m?nit s? rozd?lem teploty obou tranzistor?. |
|
| 157 |
</p> |
|
| 158 |
<p> |
|
| 159 |
Zrcadlo m??e zrcadlit referen?n? proud do v?t??ho po?tu v?stup?. Tranzistor Q2 nen? nijak |
|
| 160 |
zvl??tn?, to se jen kresl? b?ze jako by byla pr?choz? aby bylo sch?ma p?ehledn?j??. |
|
| 161 |
</p> |
|
| 162 |
<p> |
|
| 163 |
Pokud konstrukt?r integrovan?ho obvodu pot?ebuje jin? p?evodn? pom?r ne? 1:1 tak ud?l? |
|
| 164 |
n?kter? v?stupn? tranzistoru v?t?? a n?kter? men??. |
|
| 165 |
</p> |
|
| 166 |
<p> |
|
| 167 |
V?t?? tranzistor si m??eme p?edstavit jako n?kolik mal?ch tranzistor? spojen?ch paraleln?. |
|
| 168 |
Tedy i v?stupn? proud bude v?t??. |
|
| 169 |
</p> |
|
| 170 |
<p> |
|
| 171 |
<img width="212" height="250" src="pic/image011.gif" alt="Image"> |
|
| 172 |
</p> |
|
| 173 |
<p> |
|
| 174 |
Posledn? zapojen? ukazuje, jak zlep?it p?esnost zrcadlen? referen?n?ho proudu. Tranzistor |
|
| 175 |
Q3 funguje jako emitorov? sledova? a nap?j? b?ze Q1 a Q2 ani? by podstatn? u??ral |
|
| 176 |
referen?n? proud. |
|
| 177 |
</p> |
|
| 178 |
<p> |
|
| 179 |
Nap?t? na kolektoru Q1 bude cca 2x0.7V. |
|
| 180 |
</p> |
|
| 181 |
<h1> |
|
| 182 |
4. Kde se proudov? zrcadlo pou??v? |
|
| 183 |
</h1> |
|
| 184 |
<p> |
|
| 185 |
Stru?n? ?e?eno, proudov? zrcadlo se pou??v? ve v?ech analogov?ch integrovan?ch obvodech i |
|
| 186 |
v? mnoh?ch ??slicov?ch integrovan?ch obvodech. Pou?it? proudov?ho zrcadla a zdroje proudu |
|
| 187 |
jako z?t??e pro tranzistory, kter? zesiluj? u?ite?n? sign?l p?in??? obrovsk? v?hody: |
|
| 188 |
</p> |
|
| 189 |
<ul type="disc"> |
|
| 190 |
<li>Zesilova?e zesiluj? nez?visle na velikosti nap?jec?ho nap?t? |
|
| 191 |
</li> |
|
| 192 |
<li>Zesilova?e mohou zesilovat velk? sign?ly bez zkreslen? |
|
| 193 |
</li> |
|
| 194 |
<li>Rozkmit sign?l? m??e b?t t?m?? p?es cel? rozsah nap?jen? |
|
| 195 |
</li> |
|
| 196 |
<li>Obvod se obejde bez rezistor?, kter? zab?raj? velkou plochu na ?ipu |
|
| 197 |
</li> |
|
| 198 |
</ul> |
|
| 199 |
<p> |
|
| 200 |
Pod?v?me se na zapojen? jednoduch?ho kompar?toru LM339. Kompar?tor je obvod, kter? na sv?m |
|
| 201 |
v?stupu indikuje polaritu nap?t? mezi sv?mi vstupy. Velk?mu nap?t? na + vstupu odpov?d? |
|
| 202 |
velk? nap?t? na v?stupu. P?esn?ji, pokud je nap?t? na + vstupu v?t?? ne? na ? vstupu je na |
|
| 203 |
v?stupu velk? nap?t? (rozpojen? v?stupn? tranzistor) a naopak. |
|
| 204 |
</p> |
|
| 205 |
<p> |
|
| 206 |
<img width="325" height="219" src="pic/image012.jpg" alt="Image"> |
|
| 207 |
<img width="367" height="333" src="pic/image013.jpg" alt="Image"> |
|
| 208 |
</p> |
|
| 209 |
<p> |
|
| 210 |
Obvod Q13, R1, D5, D6 tvo?? jednoduch? proudov? zdroj. Proud ur?uje R1 na kter?m bude cca |
|
| 211 |
0.7V. |
|
| 212 |
</p> |
|
| 213 |
<p> |
|
| 214 |
Odpor R2 je startovac?. Bez n?ho by po zapnut? nap?jen? IO neza?al fungovat proto?e by |
|
| 215 |
v?echny tranzistory z?staly zav?en?. |
|
| 216 |
</p> |
|
| 217 |
<p> |
|
| 218 |
Tranzistory Q9, Q12, Q14 tvo?? proudov? zrcadlo a nap?j? p??slu?n? ??sti obvodu. |
|
| 219 |
</p> |
|
| 220 |
<p> |
|
| 221 |
Tranzistory Q5, Q6 jsou tak? proudov? zrcadlo a slou?? jako zat??ovac? odpory vstupn?m |
|
| 222 |
tranzistor?m Q2, Q4, kter? jsou zapojen? jako rozd?lov? zesilova?. |
|
| 223 |
</p> |
|
| 224 |
<p> |
|
| 225 |
Druh? obvod je to sam? ale z? katalogu jin?ho v?robce. ?asto se pomocn? obvody v? |
|
| 226 |
integrovan?ch obvodech kresl? zjednodu?en? nebo se nekresl? v?bec (nap??klad r?zn? ochrann? |
|
| 227 |
obvody). |
|
| 228 |
</p> |
|
| 229 |
<p> |
|
| 230 |
Proudov? zdroje r?zn? v?robci kresl? r?zn?. Tady jsou n?kter? z? b??n?ch mo?nost?: |
|
| 231 |
</p> |
|
| 232 |
<p> |
|
| 233 |
<img width="64" height="41" src="pic/image014.jpg" alt="Image"> |
|
| 234 |
<img width="68" height="40" src="pic/image015.jpg" alt="Image"> |
|
| 235 |
<img width="44" height="40" src="pic/image016.jpg" alt="Image"> |
|
| 236 |
<img width="29" height="41" src="pic/image017.jpg" alt="Image"> |
|
| 237 |
</p> |
|
| 238 |
</div> |
|
| 239 |
|
|
| 240 |
<!-- ============== PATICKA ============== --> |
|
| 241 |
<div class=Footer> |
|
| 242 |
<script type="text/javascript"> |
|
| 243 |
<!-- |
|
| 244 |
DrawFooter(); |
|
| 245 |
// --> |
|
| 246 |
</script> |
|
| 247 |
<noscript> |
|
| 248 |
<b> Pro zobrazen? (vlo?en?) hlavi?ky je pot?eba JavaScript </b> |
|
| 249 |
</noscript> |
|
| 250 |
</div> |
|
| 251 |
|
|
| 252 |
</body> |
|
| 253 |
|
|
| 254 |
</html> |
|