36:
3274:
1682:
3310:
1674:
171:
2439:
352:
93:
578:
3101:
2188:
2048:
1896:
615:
of a combination of a voltage follower driven by a voltage source with high Thévenin resistance is reduced to only the output resistance of the voltage follower (a small resistance). That resistance reduction makes the combination a more ideal voltage source. Conversely, a voltage follower inserted
277:
is very insensitive to bias changes, so any change in base voltage is transmitted (to good approximation) directly to the emitter. It depends slightly on various disturbances (transistor tolerances, temperature variations, load resistance, a collector resistor if it is added, etc.), since the
2434:{\displaystyle {\begin{aligned}R_{\text{in}}&={\frac {v_{\text{in}}}{i_{\text{b}}}}={\frac {R_{\text{S}}+r_{\pi }}{1-A_{\text{v}}}}\\&=\left(R_{\text{S}}+r_{\pi }\right)\left(1+{\frac {R_{\text{E}}}{R}}\right)\\&=R_{\text{S}}+r_{\pi }+(\beta +1)R_{\text{E}}.\end{aligned}}}
2146:
1907:
501:
1752:
3000:
2809:
1487:
567:
2918:
1624:
1552:
1409:
346:
959:
791:
2718:
1163:
1345:
1736:
1031:
420:
1912:
1229:
2193:
181:
The circuit can be explained by viewing the transistor as being under the control of negative feedback. From this viewpoint, a common-collector stage (Fig. 1) is an amplifier with full series
3085:
dominates the output impedance, which therefore also is small. A small output impedance means that the series combination of the original voltage source and the voltage follower presents a
1270:
1099:
2059:
2043:{\displaystyle {\begin{aligned}{\frac {1}{R_{\text{E}}}}&={\frac {1}{R_{\text{L}}}}+{\frac {1}{r_{\text{O}}}},\\R&={\frac {R_{\text{S}}+r_{\pi }}{\beta +1}}.\end{aligned}}}
699:
1659:
2660:
Figure 6 shows the small-signal circuit of Figure 5 with the input short-circuited and a test current placed at its output. The output resistance is found using this circuit as
859:
3089:
with a lower Thévenin resistance at its output node; that is, the combination of voltage source with voltage follower makes a more ideal voltage source than the original one.
893:
1677:
Figure 5: Small-signal circuit corresponding to Figure 3 using the hybrid-pi model for the bipolar transistor at frequencies low enough to ignore bipolar device capacitances
828:
2839:
2651:
2624:
2577:
2550:
2523:
2496:
2469:
2180:
434:
1055:
1891:{\displaystyle (\beta +1){\frac {v_{\text{in}}-v_{\text{out}}}{R_{\text{S}}+r_{\pi }}}=v_{\text{out}}\left({\frac {1}{R_{\text{L}}}}+{\frac {1}{r_{\text{O}}}}\right).}
3063:
2597:
3251:
3186:
2929:
608:
of the transistor) instead of voltage gain. A small change to the input current results in much larger change in the output current supplied to the output load.
3083:
3043:
3023:
2729:
3389:
1415:
616:
between a small load resistance and a driving stage presents a large load to the driving stage—an advantage in coupling a voltage signal to a small load.
2723:
Using Ohm's law, various currents have been found, as indicated on the diagram. Collecting the terms for the base current, the base current is found as
515:
2847:
1558:
1493:
1746:, various currents have been determined, and these results are shown on the diagram. Applying Kirchhoff's current law at the emitter one finds:
359:
A small voltage change on the input terminal will be replicated at the output (depending slightly on the transistor's gain and the value of the
2599:. That is, placing the amplifier between the load and the source presents a larger (high-resistive) load to the source than direct coupling to
1685:
Figure 6: Low-frequency small-signal circuit for bipolar voltage follower with test current at output for finding output resistance. Resistor
278:
transistor reacts to these disturbances and restores the equilibrium. It never saturates even if the input voltage reaches the positive rail.
3211:
1360:
291:
2155:) if the resistance ratio in the denominator is small. This ratio decreases with larger values of current gain β and with larger values of
908:
740:
2666:
1114:
57:
3244:
1276:
1688:
79:
965:
372:
3220:
3237:
1169:
134:
In this circuit the base terminal of the transistor serves as the input, the emitter is the output, and the collector is
706:
3203:
3358:
3280:
182:
175:
120:
50:
44:
1235:
203:(KVL) (the subtractor from the function block diagram is implemented just by the input loop), and their difference
200:
61:
3086:
2141:{\displaystyle A_{\text{v}}={\frac {v_{\text{out}}}{v_{\text{in}}}}={\frac {1}{1+{\frac {R}{R_{\text{E}}}}}}.}
1662:
612:
3318:
1061:
628:
624:
620:
147:
3368:
661:
2552:. From this result, the input resistance of the amplifier is much larger than the output load resistance
1634:
3353:
834:
1681:
865:
139:
124:
112:
797:
496:{\displaystyle r_{\text{out}}\approx {\frac {R_{\text{E}}\parallel R_{\text{source}}}{\beta _{0}}},}
3273:
3139:
702:
2817:
2629:
2602:
2555:
2528:
2501:
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2447:
2158:
3106:
900:
732:
655:
282:
1673:
1037:
3194:
1352:
627:
amplifiers. The base circuit is modified to operate the transistor in class-B or AB mode. In
509:
Typically, the emitter resistor is significantly larger and can be removed from the equation:
143:
3309:
3149:
3048:
2995:{\displaystyle R_{\text{out}}={\frac {v_{\text{x}}}{i_{\text{x}}}}=R\parallel R_{\text{E}},}
2654:
2582:
2152:
1106:
598:
590:
426:
170:
128:
651:
364:
360:
159:
2804:{\displaystyle (\beta +1)i_{\text{b}}=i_{\text{x}}-{\frac {v_{\text{x}}}{R_{\text{E}}}},}
3289:
3144:
3119:
3068:
3028:
3008:
632:
594:
582:
3383:
3327:
3134:
1482:{\displaystyle R_{\text{E}}\parallel {r_{\pi }+R_{\text{source}} \over \beta _{0}+1}}
351:
92:
3332:
3198:
3129:
589:
The common collector amplifier's low output impedance allows a source with a large
355:
Figure 3: PNP version of the emitter-follower circuit, all polarities are reversed.
151:
1743:
1742:
Figure 5 shows a low-frequency hybrid-pi model for the circuit of Figure 3. Using
3337:
3299:
3124:
3114:
597:
without changing its voltage. Thus this circuit finds applications as a voltage
155:
105:
17:
3100:
577:
3260:
3096:
611:
One aspect of buffer action is transformation of impedances. For example, the
562:{\displaystyle r_{\text{out}}\approx {\frac {R_{\text{source}}}{\beta _{0}}}.}
224:
is applied to the base–emitter junction. The transistor continuously monitors
601:. In other words, the circuit has current gain (which depends largely on the
3263:
2913:{\displaystyle v_{\text{x}}=i_{\text{b}}\left(R_{\text{S}}+r_{\pi }\right).}
1619:{\displaystyle (\beta _{0}\gg 1)\wedge (r_{\text{in}}\gg R_{\text{source}})}
1547:{\displaystyle \approx {1 \over g_{m}}+{R_{\text{source}} \over \beta _{0}}}
363:; see gain formula below). This circuit is useful because it has a large
3229:
2841:
is defined above. Using this value for base current, Ohm's law provides
3363:
1404:{\displaystyle r_{\text{out}}={\frac {v_{\text{out}}}{i_{\text{out}}}}}
341:{\displaystyle A_{v}={\frac {v_{\text{out}}}{v_{\text{in}}}}\approx 1.}
185:. In this configuration (Fig. 2 with β = 1), the entire output voltage
97:
3168:
954:{\displaystyle A_{\mathrm {v} }={v_{\text{out}} \over v_{\text{in}}}}
786:{\displaystyle A_{\mathrm {i} }={i_{\text{out}} \over i_{\text{in}}}}
2713:{\displaystyle R_{\text{out}}={\frac {v_{\text{x}}}{i_{\text{x}}}}.}
1158:{\displaystyle r_{\text{in}}={\frac {v_{\text{in}}}{i_{\text{in}}}}}
270:
Intuitively, this behavior can be also understood by realizing that
2626:, which results in less signal attenuation in the source impedance
281:
The common-collector circuit can be shown mathematically to have a
169:
91:
1340:{\displaystyle (g_{m}R_{\text{E}}\gg 1)\wedge (\beta _{0}\gg 1)}
3233:
2151:
From this result, the gain approaches unity (as expected for a
1731:{\displaystyle R_{\text{E}}=R_{\text{L}}\parallel r_{\text{O}}}
245:
by passing the collector current through the emitter resistor R
29:
1026:{\displaystyle {g_{m}R_{\text{E}} \over g_{m}R_{\text{E}}+1}}
619:
This configuration is commonly used in the output stages of
415:{\displaystyle r_{\text{in}}\approx \beta _{0}R_{\text{E}},}
425:
so it will not load down the previous circuit, and a small
2923:
Substituting for the base current, and collecting terms,
96:
Figure 1: Basic NPN common collector circuit (neglecting
192:
is placed contrary and in series with the input voltage
3045:
generally is a small resistance when the current gain
3204:
Theodore Pavlic: ECE 327: Transistor Basics; part 6:
3071:
3051:
3031:
3011:
2932:
2850:
2820:
2732:
2669:
2632:
2605:
2585:
2558:
2531:
2504:
2477:
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2191:
2161:
2062:
1910:
1755:
1691:
1637:
1561:
1496:
1418:
1363:
1279:
1238:
1224:{\displaystyle r_{\pi }+(\beta _{0}+1)R_{\text{E}}\ }
1172:
1117:
1064:
1040:
968:
911:
868:
837:
800:
743:
664:
518:
437:
375:
294:
199:. Thus the two voltages are subtracted according to
3346:
3317:
3279:
3077:
3057:
3037:
3017:
2994:
2912:
2833:
2803:
2712:
2645:
2618:
2591:
2571:
2544:
2517:
2490:
2463:
2433:
2174:
2140:
2042:
1890:
1730:
1653:
1618:
1546:
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1403:
1339:
1264:
1223:
1157:
1093:
1049:
1025:
953:
887:
853:
822:
785:
693:
561:
495:
414:
340:
2053:Then collecting terms the voltage gain is found:
642:(Fig. 4) to improve linearity and/or efficiency.
1265:{\displaystyle \approx \beta _{0}R_{\text{E}}}
3245:
8:
3005:where || denotes a parallel connection, and
658:characteristics can be derived. (Parameter
3252:
3238:
3230:
650:At low frequencies and using a simplified
3070:
3050:
3030:
3010:
2983:
2962:
2952:
2946:
2937:
2931:
2896:
2883:
2868:
2855:
2849:
2825:
2819:
2790:
2780:
2774:
2765:
2752:
2731:
2699:
2689:
2683:
2674:
2668:
2637:
2631:
2610:
2604:
2584:
2563:
2557:
2536:
2530:
2509:
2503:
2482:
2476:
2471:ordinarily is large compared to the load
2455:
2449:
2418:
2390:
2377:
2347:
2341:
2319:
2306:
2278:
2260:
2247:
2240:
2229:
2219:
2213:
2200:
2192:
2190:
2166:
2160:
2124:
2115:
2103:
2092:
2082:
2076:
2067:
2061:
2013:
2000:
1993:
1968:
1959:
1948:
1939:
1924:
1915:
1911:
1909:
1872:
1863:
1852:
1843:
1832:
1816:
1803:
1791:
1778:
1771:
1754:
1722:
1709:
1696:
1690:
1642:
1636:
1607:
1594:
1569:
1560:
1536:
1526:
1520:
1509:
1500:
1495:
1464:
1452:
1439:
1432:
1423:
1417:
1393:
1383:
1377:
1368:
1362:
1322:
1297:
1287:
1278:
1256:
1246:
1237:
1212:
1193:
1177:
1171:
1147:
1137:
1131:
1122:
1116:
1079:
1069:
1063:
1039:
1008:
998:
986:
976:
969:
967:
943:
933:
927:
917:
916:
910:
873:
867:
845:
836:
805:
799:
775:
765:
759:
749:
748:
742:
685:
675:
663:
548:
538:
532:
523:
517:
482:
471:
458:
451:
442:
436:
403:
393:
380:
374:
324:
314:
308:
299:
293:
231:and adjusts its emitter voltage to equal
80:Learn how and when to remove this message
1901:Define the following resistance values:
1680:
1672:
711:
585:biasing suitable for integrated circuits
576:
350:
138:to both (for example, it may be tied to
43:This article includes a list of general
3161:
1094:{\displaystyle g_{m}R_{\text{E}}\gg 1}
506:so it can drive low-resistance loads.
267:; hence the name "emitter follower".
119:) is one of three basic single-stage
7:
694:{\displaystyle \beta =g_{m}r_{\pi }}
581:Figure 4: NPN voltage follower with
2182:. The input resistance is found as
1654:{\displaystyle R_{\text{source}}\ }
3390:Single-stage transistor amplifiers
3189:Basic BJT Amplifier Configurations
918:
854:{\displaystyle \approx \beta _{0}}
750:
253:the input voltage variations from
249:. As a result, the output voltage
49:it lacks sufficient corresponding
25:
2444:The transistor output resistance
146:), hence its name. The analogous
3308:
3272:
3099:
34:
3171:20 Watt Class-A Power Amplifier
888:{\displaystyle \beta _{0}\gg 1}
3214:The common collector amplifier
3195:NPN Common Collector Amplifier
2745:
2733:
2411:
2399:
1768:
1756:
1665:equivalent source resistance.
1613:
1587:
1581:
1562:
1334:
1315:
1309:
1280:
1205:
1186:
823:{\displaystyle \beta _{0}+1\ }
1:
2834:{\displaystyle R_{\text{E}}}
2646:{\displaystyle R_{\text{S}}}
2619:{\displaystyle R_{\text{L}}}
2572:{\displaystyle R_{\text{L}}}
2545:{\displaystyle R_{\text{E}}}
2518:{\displaystyle R_{\text{L}}}
2491:{\displaystyle R_{\text{L}}}
2464:{\displaystyle r_{\text{O}}}
2175:{\displaystyle R_{\text{E}}}
154:amplifier and the analogous
27:Type of transistor amplifier
3359:Complementary feedback pair
3281:Bipolar junction transistor
176:negative-feedback amplifier
121:bipolar junction transistor
3406:
3025:is defined above. Because
631:mode, sometimes an active
238:minus the mostly constant
3306:
3270:
1050:{\displaystyle \approx 1}
3319:Field-effect transistor
3087:Thévenin voltage source
2579:for large current gain
723:Approximate expression
201:Kirchhoff's voltage law
148:field-effect transistor
64:more precise citations.
3079:
3059:
3058:{\displaystyle \beta }
3039:
3019:
2996:
2914:
2835:
2805:
2714:
2647:
2620:
2593:
2592:{\displaystyle \beta }
2573:
2546:
2519:
2492:
2465:
2435:
2176:
2142:
2044:
1892:
1739:
1732:
1678:
1655:
1620:
1548:
1483:
1405:
1341:
1266:
1225:
1159:
1095:
1051:
1027:
955:
889:
855:
824:
787:
707:components in parallel
695:
586:
563:
497:
416:
356:
342:
178:
127:, typically used as a
101:
3354:Darlington transistor
3347:Multiple transistors:
3080:
3060:
3040:
3020:
2997:
2915:
2836:
2806:
2715:
2648:
2621:
2594:
2574:
2547:
2520:
2493:
2466:
2436:
2177:
2143:
2045:
1893:
1733:
1684:
1676:
1656:
1621:
1549:
1484:
1406:
1342:
1267:
1226:
1160:
1096:
1052:
1028:
956:
890:
856:
825:
788:
696:
580:
564:
498:
417:
354:
343:
173:
95:
3206:npn Emitter Follower
3069:
3049:
3029:
3009:
2930:
2848:
2818:
2730:
2667:
2653:as a consequence of
2630:
2603:
2583:
2556:
2529:
2502:
2475:
2448:
2189:
2159:
2060:
1908:
1753:
1689:
1635:
1559:
1494:
1416:
1361:
1277:
1236:
1170:
1115:
1062:
1038:
966:
909:
866:
835:
798:
741:
662:
516:
435:
373:
292:
3140:IC power-supply pin
635:is used instead of
613:Thévenin resistance
3107:Electronics portal
3075:
3055:
3035:
3015:
2992:
2910:
2831:
2801:
2710:
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2616:
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2542:
2515:
2488:
2461:
2431:
2429:
2172:
2138:
2040:
2038:
1888:
1740:
1728:
1679:
1651:
1616:
1544:
1479:
1401:
1337:
1262:
1221:
1155:
1091:
1047:
1023:
951:
885:
851:
820:
783:
691:
587:
559:
493:
412:
357:
338:
179:
115:(also known as an
102:
3377:
3376:
3078:{\displaystyle R}
3038:{\displaystyle R}
3018:{\displaystyle R}
2986:
2968:
2965:
2955:
2940:
2886:
2871:
2858:
2828:
2796:
2793:
2783:
2768:
2755:
2705:
2702:
2692:
2677:
2640:
2613:
2566:
2539:
2512:
2485:
2458:
2421:
2380:
2356:
2350:
2309:
2285:
2281:
2250:
2235:
2232:
2222:
2203:
2169:
2133:
2130:
2127:
2098:
2095:
2085:
2070:
2031:
2003:
1974:
1971:
1954:
1951:
1930:
1927:
1878:
1875:
1858:
1855:
1835:
1823:
1806:
1794:
1781:
1725:
1712:
1699:
1650:
1645:
1629:
1628:
1610:
1597:
1542:
1529:
1515:
1477:
1455:
1426:
1399:
1396:
1386:
1371:
1353:Output resistance
1300:
1259:
1220:
1215:
1153:
1150:
1140:
1125:
1082:
1021:
1011:
989:
949:
946:
936:
819:
781:
778:
768:
593:to drive a small
554:
541:
526:
488:
474:
461:
445:
406:
383:
330:
327:
317:
285:of almost unity:
183:negative feedback
144:power supply rail
90:
89:
82:
16:(Redirected from
3397:
3369:Long-tailed pair
3312:
3295:Common collector
3276:
3254:
3247:
3240:
3231:
3187:R Victor Jones:
3174:
3166:
3150:Two-port network
3109:
3104:
3103:
3084:
3082:
3081:
3076:
3064:
3062:
3061:
3056:
3044:
3042:
3041:
3036:
3024:
3022:
3021:
3016:
3001:
2999:
2998:
2993:
2988:
2987:
2984:
2969:
2967:
2966:
2963:
2957:
2956:
2953:
2947:
2942:
2941:
2938:
2919:
2917:
2916:
2911:
2906:
2902:
2901:
2900:
2888:
2887:
2884:
2873:
2872:
2869:
2860:
2859:
2856:
2840:
2838:
2837:
2832:
2830:
2829:
2826:
2810:
2808:
2807:
2802:
2797:
2795:
2794:
2791:
2785:
2784:
2781:
2775:
2770:
2769:
2766:
2757:
2756:
2753:
2719:
2717:
2716:
2711:
2706:
2704:
2703:
2700:
2694:
2693:
2690:
2684:
2679:
2678:
2675:
2655:voltage division
2652:
2650:
2649:
2644:
2642:
2641:
2638:
2625:
2623:
2622:
2617:
2615:
2614:
2611:
2598:
2596:
2595:
2590:
2578:
2576:
2575:
2570:
2568:
2567:
2564:
2551:
2549:
2548:
2543:
2541:
2540:
2537:
2524:
2522:
2521:
2516:
2514:
2513:
2510:
2498:, and therefore
2497:
2495:
2494:
2489:
2487:
2486:
2483:
2470:
2468:
2467:
2462:
2460:
2459:
2456:
2440:
2438:
2437:
2432:
2430:
2423:
2422:
2419:
2395:
2394:
2382:
2381:
2378:
2366:
2362:
2358:
2357:
2352:
2351:
2348:
2342:
2329:
2325:
2324:
2323:
2311:
2310:
2307:
2290:
2286:
2284:
2283:
2282:
2279:
2266:
2265:
2264:
2252:
2251:
2248:
2241:
2236:
2234:
2233:
2230:
2224:
2223:
2220:
2214:
2205:
2204:
2201:
2181:
2179:
2178:
2173:
2171:
2170:
2167:
2153:buffer amplifier
2147:
2145:
2144:
2139:
2134:
2132:
2131:
2129:
2128:
2125:
2116:
2104:
2099:
2097:
2096:
2093:
2087:
2086:
2083:
2077:
2072:
2071:
2068:
2049:
2047:
2046:
2041:
2039:
2032:
2030:
2019:
2018:
2017:
2005:
2004:
2001:
1994:
1975:
1973:
1972:
1969:
1960:
1955:
1953:
1952:
1949:
1940:
1931:
1929:
1928:
1925:
1916:
1897:
1895:
1894:
1889:
1884:
1880:
1879:
1877:
1876:
1873:
1864:
1859:
1857:
1856:
1853:
1844:
1837:
1836:
1833:
1824:
1822:
1821:
1820:
1808:
1807:
1804:
1797:
1796:
1795:
1792:
1783:
1782:
1779:
1772:
1737:
1735:
1734:
1729:
1727:
1726:
1723:
1714:
1713:
1710:
1701:
1700:
1697:
1660:
1658:
1657:
1652:
1648:
1647:
1646:
1643:
1625:
1623:
1622:
1617:
1612:
1611:
1608:
1599:
1598:
1595:
1574:
1573:
1553:
1551:
1550:
1545:
1543:
1541:
1540:
1531:
1530:
1527:
1521:
1516:
1514:
1513:
1501:
1488:
1486:
1485:
1480:
1478:
1476:
1469:
1468:
1458:
1457:
1456:
1453:
1444:
1443:
1433:
1428:
1427:
1424:
1410:
1408:
1407:
1402:
1400:
1398:
1397:
1394:
1388:
1387:
1384:
1378:
1373:
1372:
1369:
1346:
1344:
1343:
1338:
1327:
1326:
1302:
1301:
1298:
1292:
1291:
1271:
1269:
1268:
1263:
1261:
1260:
1257:
1251:
1250:
1230:
1228:
1227:
1222:
1218:
1217:
1216:
1213:
1198:
1197:
1182:
1181:
1164:
1162:
1161:
1156:
1154:
1152:
1151:
1148:
1142:
1141:
1138:
1132:
1127:
1126:
1123:
1107:Input resistance
1100:
1098:
1097:
1092:
1084:
1083:
1080:
1074:
1073:
1056:
1054:
1053:
1048:
1032:
1030:
1029:
1024:
1022:
1020:
1013:
1012:
1009:
1003:
1002:
992:
991:
990:
987:
981:
980:
970:
960:
958:
957:
952:
950:
948:
947:
944:
938:
937:
934:
928:
923:
922:
921:
894:
892:
891:
886:
878:
877:
860:
858:
857:
852:
850:
849:
829:
827:
826:
821:
817:
810:
809:
792:
790:
789:
784:
782:
780:
779:
776:
770:
769:
766:
760:
755:
754:
753:
712:
700:
698:
697:
692:
690:
689:
680:
679:
654:, the following
591:output impedance
568:
566:
565:
560:
555:
553:
552:
543:
542:
539:
533:
528:
527:
524:
502:
500:
499:
494:
489:
487:
486:
477:
476:
475:
472:
463:
462:
459:
452:
447:
446:
443:
427:output impedance
421:
419:
418:
413:
408:
407:
404:
398:
397:
385:
384:
381:
347:
345:
344:
339:
331:
329:
328:
325:
319:
318:
315:
309:
304:
303:
160:cathode follower
140:ground reference
123:(BJT) amplifier
117:emitter follower
110:common collector
85:
78:
74:
71:
65:
60:this article by
51:inline citations
38:
37:
30:
21:
18:Emitter follower
3405:
3404:
3400:
3399:
3398:
3396:
3395:
3394:
3380:
3379:
3378:
3373:
3342:
3313:
3304:
3277:
3266:
3258:
3212:Doug Gingrich:
3183:
3178:
3177:
3167:
3163:
3158:
3105:
3098:
3095:
3067:
3066:
3047:
3046:
3027:
3026:
3007:
3006:
2979:
2958:
2948:
2933:
2928:
2927:
2892:
2879:
2878:
2874:
2864:
2851:
2846:
2845:
2821:
2816:
2815:
2786:
2776:
2761:
2748:
2728:
2727:
2695:
2685:
2670:
2665:
2664:
2633:
2628:
2627:
2606:
2601:
2600:
2581:
2580:
2559:
2554:
2553:
2532:
2527:
2526:
2505:
2500:
2499:
2478:
2473:
2472:
2451:
2446:
2445:
2428:
2427:
2414:
2386:
2373:
2364:
2363:
2343:
2334:
2330:
2315:
2302:
2301:
2297:
2288:
2287:
2274:
2267:
2256:
2243:
2242:
2225:
2215:
2206:
2196:
2187:
2186:
2162:
2157:
2156:
2120:
2108:
2088:
2078:
2063:
2058:
2057:
2037:
2036:
2020:
2009:
1996:
1995:
1986:
1980:
1979:
1964:
1944:
1932:
1920:
1906:
1905:
1868:
1848:
1842:
1838:
1828:
1812:
1799:
1798:
1787:
1774:
1773:
1751:
1750:
1718:
1705:
1692:
1687:
1686:
1671:
1638:
1633:
1632:
1603:
1590:
1565:
1557:
1556:
1532:
1522:
1505:
1492:
1491:
1460:
1459:
1448:
1435:
1434:
1419:
1414:
1413:
1389:
1379:
1364:
1359:
1358:
1318:
1293:
1283:
1275:
1274:
1252:
1242:
1234:
1233:
1208:
1189:
1173:
1168:
1167:
1143:
1133:
1118:
1113:
1112:
1075:
1065:
1060:
1059:
1036:
1035:
1004:
994:
993:
982:
972:
971:
964:
963:
939:
929:
912:
907:
906:
869:
864:
863:
841:
833:
832:
801:
796:
795:
771:
761:
744:
739:
738:
705:lines indicate
681:
671:
660:
659:
652:hybrid-pi model
648:
646:Characteristics
641:
607:
575:
544:
534:
519:
514:
513:
478:
467:
454:
453:
438:
433:
432:
399:
389:
376:
371:
370:
365:input impedance
361:load resistance
320:
310:
295:
290:
289:
276:
266:
259:
248:
244:
237:
230:
223:
216:
209:
198:
191:
168:
158:circuit is the
150:circuit is the
86:
75:
69:
66:
56:Please help to
55:
39:
35:
28:
23:
22:
15:
12:
11:
5:
3403:
3401:
3393:
3392:
3382:
3381:
3375:
3374:
3372:
3371:
3366:
3361:
3356:
3350:
3348:
3344:
3343:
3341:
3340:
3335:
3330:
3324:
3322:
3315:
3314:
3307:
3305:
3303:
3302:
3297:
3292:
3290:Common emitter
3286:
3284:
3278:
3271:
3268:
3267:
3259:
3257:
3256:
3249:
3242:
3234:
3228:
3227:
3221:Raymond Frey:
3218:
3209:
3201:
3192:
3182:
3181:External links
3179:
3176:
3175:
3160:
3159:
3157:
3154:
3153:
3152:
3147:
3145:Open collector
3142:
3137:
3132:
3127:
3122:
3120:Common emitter
3117:
3111:
3110:
3094:
3091:
3074:
3054:
3034:
3014:
3003:
3002:
2991:
2982:
2978:
2975:
2972:
2961:
2951:
2945:
2936:
2921:
2920:
2909:
2905:
2899:
2895:
2891:
2882:
2877:
2867:
2863:
2854:
2824:
2812:
2811:
2800:
2789:
2779:
2773:
2764:
2760:
2751:
2747:
2744:
2741:
2738:
2735:
2721:
2720:
2709:
2698:
2688:
2682:
2673:
2636:
2609:
2588:
2562:
2535:
2508:
2481:
2454:
2442:
2441:
2426:
2417:
2413:
2410:
2407:
2404:
2401:
2398:
2393:
2389:
2385:
2376:
2372:
2369:
2367:
2365:
2361:
2355:
2346:
2340:
2337:
2333:
2328:
2322:
2318:
2314:
2305:
2300:
2296:
2293:
2291:
2289:
2277:
2273:
2270:
2263:
2259:
2255:
2246:
2239:
2228:
2218:
2212:
2209:
2207:
2199:
2195:
2194:
2165:
2149:
2148:
2137:
2123:
2119:
2114:
2111:
2107:
2102:
2091:
2081:
2075:
2066:
2051:
2050:
2035:
2029:
2026:
2023:
2016:
2012:
2008:
1999:
1992:
1989:
1987:
1985:
1982:
1981:
1978:
1967:
1963:
1958:
1947:
1943:
1938:
1935:
1933:
1923:
1919:
1914:
1913:
1899:
1898:
1887:
1883:
1871:
1867:
1862:
1851:
1847:
1841:
1831:
1827:
1819:
1815:
1811:
1802:
1790:
1786:
1777:
1770:
1767:
1764:
1761:
1758:
1721:
1717:
1708:
1704:
1695:
1670:
1667:
1641:
1627:
1626:
1615:
1606:
1602:
1593:
1589:
1586:
1583:
1580:
1577:
1572:
1568:
1564:
1554:
1539:
1535:
1525:
1519:
1512:
1508:
1504:
1499:
1489:
1475:
1472:
1467:
1463:
1451:
1447:
1442:
1438:
1431:
1422:
1411:
1392:
1382:
1376:
1367:
1356:
1348:
1347:
1336:
1333:
1330:
1325:
1321:
1317:
1314:
1311:
1308:
1305:
1296:
1290:
1286:
1282:
1272:
1255:
1249:
1245:
1241:
1231:
1211:
1207:
1204:
1201:
1196:
1192:
1188:
1185:
1180:
1176:
1165:
1146:
1136:
1130:
1121:
1110:
1102:
1101:
1090:
1087:
1078:
1072:
1068:
1057:
1046:
1043:
1033:
1019:
1016:
1007:
1001:
997:
985:
979:
975:
961:
942:
932:
926:
920:
915:
904:
896:
895:
884:
881:
876:
872:
861:
848:
844:
840:
830:
816:
813:
808:
804:
793:
774:
764:
758:
752:
747:
736:
728:
727:
724:
721:
718:
715:
688:
684:
678:
674:
670:
667:
647:
644:
639:
633:current source
605:
595:load impedance
583:current source
574:
571:
570:
569:
558:
551:
547:
537:
531:
522:
504:
503:
492:
485:
481:
470:
466:
457:
450:
441:
423:
422:
411:
402:
396:
392:
388:
379:
349:
348:
337:
334:
323:
313:
307:
302:
298:
274:
264:
257:
246:
242:
235:
228:
221:
214:
207:
196:
189:
167:
164:
129:voltage buffer
88:
87:
42:
40:
33:
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
3402:
3391:
3388:
3387:
3385:
3370:
3367:
3365:
3362:
3360:
3357:
3355:
3352:
3351:
3349:
3345:
3339:
3336:
3334:
3331:
3329:
3328:Common source
3326:
3325:
3323:
3320:
3316:
3311:
3301:
3298:
3296:
3293:
3291:
3288:
3287:
3285:
3282:
3275:
3269:
3265:
3262:
3255:
3250:
3248:
3243:
3241:
3236:
3235:
3232:
3226:
3224:
3223:Lab exercises
3219:
3217:
3216:U of Alberta
3215:
3210:
3208:
3207:
3202:
3200:
3196:
3193:
3191:
3190:
3185:
3184:
3180:
3173:
3172:
3165:
3162:
3155:
3151:
3148:
3146:
3143:
3141:
3138:
3136:
3135:Common source
3133:
3131:
3128:
3126:
3123:
3121:
3118:
3116:
3113:
3112:
3108:
3102:
3097:
3092:
3090:
3088:
3072:
3052:
3032:
3012:
2989:
2980:
2976:
2973:
2970:
2959:
2949:
2943:
2934:
2926:
2925:
2924:
2907:
2903:
2897:
2893:
2889:
2880:
2875:
2865:
2861:
2852:
2844:
2843:
2842:
2822:
2798:
2787:
2777:
2771:
2762:
2758:
2749:
2742:
2739:
2736:
2726:
2725:
2724:
2707:
2696:
2686:
2680:
2671:
2663:
2662:
2661:
2658:
2656:
2634:
2607:
2586:
2560:
2533:
2506:
2479:
2452:
2424:
2415:
2408:
2405:
2402:
2396:
2391:
2387:
2383:
2374:
2370:
2368:
2359:
2353:
2344:
2338:
2335:
2331:
2326:
2320:
2316:
2312:
2303:
2298:
2294:
2292:
2275:
2271:
2268:
2261:
2257:
2253:
2244:
2237:
2226:
2216:
2210:
2208:
2197:
2185:
2184:
2183:
2163:
2154:
2135:
2121:
2117:
2112:
2109:
2105:
2100:
2089:
2079:
2073:
2064:
2056:
2055:
2054:
2033:
2027:
2024:
2021:
2014:
2010:
2006:
1997:
1990:
1988:
1983:
1976:
1965:
1961:
1956:
1945:
1941:
1936:
1934:
1921:
1917:
1904:
1903:
1902:
1885:
1881:
1869:
1865:
1860:
1849:
1845:
1839:
1829:
1825:
1817:
1813:
1809:
1800:
1788:
1784:
1775:
1765:
1762:
1759:
1749:
1748:
1747:
1745:
1719:
1715:
1706:
1702:
1693:
1683:
1675:
1668:
1666:
1664:
1639:
1604:
1600:
1591:
1584:
1578:
1575:
1570:
1566:
1555:
1537:
1533:
1523:
1517:
1510:
1506:
1502:
1497:
1490:
1473:
1470:
1465:
1461:
1449:
1445:
1440:
1436:
1429:
1420:
1412:
1390:
1380:
1374:
1365:
1357:
1355:
1354:
1350:
1349:
1331:
1328:
1323:
1319:
1312:
1306:
1303:
1294:
1288:
1284:
1273:
1253:
1247:
1243:
1239:
1232:
1209:
1202:
1199:
1194:
1190:
1183:
1178:
1174:
1166:
1144:
1134:
1128:
1119:
1111:
1109:
1108:
1104:
1103:
1088:
1085:
1076:
1070:
1066:
1058:
1044:
1041:
1034:
1017:
1014:
1005:
999:
995:
983:
977:
973:
962:
940:
930:
924:
913:
905:
903:
902:
898:
897:
882:
879:
874:
870:
862:
846:
842:
838:
831:
814:
811:
806:
802:
794:
772:
762:
756:
745:
737:
735:
734:
730:
729:
725:
722:
719:
716:
714:
713:
710:
708:
704:
686:
682:
676:
672:
668:
665:
657:
653:
645:
643:
638:
634:
630:
626:
622:
617:
614:
609:
604:
600:
596:
592:
584:
579:
572:
556:
549:
545:
535:
529:
520:
512:
511:
510:
507:
490:
483:
479:
468:
464:
455:
448:
439:
431:
430:
429:
428:
409:
400:
394:
390:
386:
377:
369:
368:
367:
366:
362:
353:
335:
332:
321:
311:
305:
300:
296:
288:
287:
286:
284:
279:
273:
268:
263:
256:
252:
241:
234:
227:
220:
213:
206:
202:
195:
188:
184:
177:
172:
166:Basic circuit
165:
163:
161:
157:
153:
149:
145:
141:
137:
132:
130:
126:
122:
118:
114:
111:
107:
99:
94:
84:
81:
73:
63:
59:
53:
52:
46:
41:
32:
31:
19:
3333:Common drain
3294:
3222:
3213:
3205:
3199:HyperPhysics
3188:
3170:
3169:Rod Elliot:
3164:
3130:Common drain
3004:
2922:
2813:
2722:
2659:
2443:
2150:
2052:
1900:
1741:
1630:
1351:
1105:
901:Voltage gain
899:
733:Current gain
731:
656:small-signal
649:
636:
618:
610:
602:
588:
573:Applications
508:
505:
424:
358:
283:voltage gain
280:
271:
269:
261:
254:
250:
239:
232:
225:
218:
211:
204:
193:
186:
180:
174:Figure 2: A
152:common drain
135:
133:
116:
109:
103:
76:
67:
48:
3338:Common gate
3300:Common base
3225:U of Oregon
3125:Common gate
3115:Common base
1669:Derivations
726:Conditions
720:Expression
717:Definition
106:electronics
62:introducing
3264:amplifiers
3261:Transistor
3156:References
3065:is large,
2525:dominates
125:topologies
70:April 2009
45:references
3053:β
2977:∥
2898:π
2772:−
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2403:β
2392:π
2321:π
2272:−
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2022:β
2015:π
1818:π
1785:−
1760:β
1744:Ohm's law
1716:∥
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1585:∧
1576:≫
1567:β
1534:β
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1462:β
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1320:β
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1042:≈
880:≫
871:β
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839:≈
803:β
687:π
666:β
546:β
530:≈
480:β
465:∥
449:≈
391:β
387:≈
333:≈
113:amplifier
100:details).
3384:Category
3093:See also
1663:Thévenin
703:parallel
701:and the
625:class-AB
3364:Cascode
1661:is the
629:class-A
621:class-B
251:follows
98:biasing
58:improve
2814:where
1649:
1644:source
1631:Where
1609:source
1528:source
1454:source
1219:
818:
599:buffer
540:source
473:source
260:up to
136:common
47:, but
142:or a
623:and
229:diff
208:diff
156:tube
108:, a
2939:out
2676:out
2084:out
1834:out
1793:out
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767:out
709:.)
525:out
444:out
316:out
222:out
190:out
104:In
3386::
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77:(
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