V d. V or lower than the. +V p R 3. V o R 2 R 1. -V n. PHYSICS 536 Experiment 7: Transistor Biasing Equation Chapter 7 Section 1

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1 PHYSCS 536 Experiment 7: ranitor Biaing Equation Chapter 7 Setion Appropriate DC operating onition mut e etalihe for any iruit efore it an e ue to repon to an input ignal. hee are alle the ia or quieent onition (i.e., without an input ignal). he quieent urrent an voltage in the iruit mut permit the expete hange to our without getting the tranitor out of it normal operating range. hi experiment involve only DC meaurement, however we till ue ypa apaitor eaue AC ignal an itort DC meaurement. Refer to GL etion 3.2 an 3. for further intrution. Rememer to turn off the voltage upplie efore omponent are hange. A. heoretial Summary he quieent rain voltage ( ) etermine the + p maximum poile hange in rain voltage. annot go higher than or lower than the p minimum voltage neee to operate the FE. o he minimum voltage i equal to eaue the gate i at zero volt in thi iruit, reall that = ( )/2R. he two following p 3 equation expre the maximum poile rain variation are + ( ) p an R 2 R - n ( ). hee limit retrit the amplitue of the output ignal, o. he value of i etermine y the voltage rop aro = R (.) p 3

2 he maximum amplitue i otaine for a ine wave when the poitive an negative limit are equal. i then given y the following relation: = ( )/2R (.2) p n = 0 R. Self-Bia for a FE,. he value of neee to otain the eire / 2 / [ ( / ) ] 3 i: R = (.3) n 2. Controlle Biaing, i nonzero. he urrent i muh le epenent on tranitor parameter when a iaing voltage, n, an a larger erie reitor, rain urrent i given y R, are ue. he = ( )/R (.4) g n When g i not negligile ompare to, it an e etimate uing the following n equation. /2 g = [ ( / ) ] (.5) g 0.3 when /2 n BJ iruit, e an uually e etimate y 0.6, ut it may e neeary to inlue the voltage rop aro R. he olletor urrent i then given y n = R + R / h 2 fe (.6) When a voltage ivier i ue to lift the ae of a BJ aove ommon, it may e neeary to inlue the effet of ae urrent to alulate the ae voltage. he ae voltage i then given y ( R r ) 2 = p ( R + ( 4 R 2 r )) (.7)

3 r h R fe (.8) A uual, the BJ urrent i etermine y the voltage aro the reitor R in erie the emitter. = ( 0.6 )/ R he equivalent hange in ae-emitter voltage ( H ue to heating in a BJ i, ) When = C = C ( θ P) = C ( θ ) H JA JA C = 2 m /egreec i hel approximately ontant, y uing a large value for R, i oerve a a hange in. ereae when the temperature inreae. e e B. Simplifie Meaurement for an H A multi-meter an e ue to meaure with the oure. an eaily y inerting the meter in erie + he long meter lea an aue the FE to oillate unle a y-pa apaitor i ue at the oure. he oure voltage i etermine y the FE urrent through the internal reitane, R, of the meter. m g = Rm C / Multimeter he oure voltage annot e larger than eaue that i the value that reue C = 0. µf to zero. When the meter i et to rea voltage, = = 0.9 R i very high, hene m mall, whih mean that the meter reaing will e approximately equal to meter g Meter on voltage ale. will e very

4 A 0% orretion i inlue eaue i lightly larger than zero. R i very mall m when the meter i on the urrent ale, hene i approximately zero, whih mean that =. meter = = Meter on urrent ale hi i a very ueful proeure, eaue the ai FE parameter an e meaure uing only a voltage oure an a - meter. (A 9 attery will o if you on t have a power upply availale) - Ue thi proe ure to meaure an the rain voltage. g for a FE. Ue the power upply for C. Self-Biaing of a JFE ypial value an ata from the evie peifiation for an will e ue to alulate ia onition for homework. he meaure value of thee parameter from tep will e ue to alulate oervale in la. 2 - Ue the typial an omponent heet. Calulate the given on the neee to et the quieent rain voltage ( ) half way etween the power upply volta ge ( p ) an D + p + D MPF02 the minimum voltage ( m) neee y FE. ( m = in thi iruit eaue Ue equation (.4) to alulate the to otain thi = 0) g. Calulate the maximum amplitue (peak-peak), unitorte ine wave that oul e otaine at the rain. nlue thee alulation in your laoratory report. R neee 3 - Ue the meaure value from tep in the proe erie in tep 2 to alulate R. Ue equation (.5) to alulate the expete R. Ue the reitor value

5 for R that i loet to the alulate value. Meaure an an ompare to that expete. D. Controlle FE Biaing Better ontrol of an e otaine y onn eting the lower en of to a negative power upply ( ) n rather than to groun. (he gate tay onnete to groun.) n thi R arrangement i ontrolle primarily y an R, ut the extrem of n e mut e oniere unle i muh greater than. n 4 - nlue in your laoratory report the following alulation. hi iruit houl have the ame an a tep 2. Ue the ame typial an. Ue eqn. (.5) to alulate. Alo alulate g Next we will ee what effet ifferent FE R. parameter woul have on the quieent onition. Calulate an if the FE ha the maximum + g + p D R + p an given in the pe heet. Ue the otaine with typial parameter in the firt part of thi prolem a an etimate for the new in eqn. (.5), whih in turn i ue to etimate the new. hi etimate i aequate eaue g R prevent from hanging ramatially. Repeat for the minimum parameter given in the pe heet. When, i relatively inepenent of the FE parameter eaue they only affet n g. g 5 - Ue a 5% reitor that i nearet to the value of R alulate in tep 4. will e approximately the ame a that alulate in tep 3 eaue the iruit i eigne to have the ame. Meaure an an ompare to the expete value.

6 6 - Oerve with a meter while you vary from 0 to 25 volt. You will ee that n hange a neeary o that the hannel an onut the urrent flowing through wor. R. Give a rief explanation of how thi elf-ajutment our in your own 7 - nlue in your laoratory report the following alulation. he ojet i to et the quieent poitive pule. to otain a maximum poitive hange at the rain i.e. v i a houl e elete o that there will e aequate rain voltage for the FE. Next alulate g = (max). What value of = (max). hen in the wort ae R etimating woul our with thi R if an were the minimum? What limit woul e impoe on the amplitue of meaurement require. v? No at E. Controlle BJ Biaing Although the iruit ue here i imilar to that in the preeing etion, rememer that the pin orer on the BJ an FE are not the ame. Firt, a mall will e ue o that it oen t affet the meaurement. hen R 2 R will e larger o that it ha an effet. 2 8 Uing the peifie parameter in tep 8 alulate, e in your laoratory report. alulation.,,, an, inlue thee 9 Change the value of R 2 an repeat thee 0 - Ue the igital meter to meaure the voltage peifie in tep 8 an 9. F. Controlle BJ Biaing with a oltage Divier R 2 + p 2N3904 R - n

7 + p he avantage of ontrolle iaing an e otaine with a ingle power upply y uing a voltage ivier to et the DC voltage at the input. he alulation are imple for a FE eaue it gate urrent i negligile, ut the ae urrent of a BJ an affet he ivier. Firt we onier a ae where the ivier reitor are mall, ivier urrent large, o that an e neglete. Next we inreae the ivier reitor to otain a higher reitane at the input an inlue the effet of on. R 4 R 2 B 2N3904 R - Calulate,, an an inlue thee in your laoratory report. What i the maximum poitive an negative hange availale at the olletor? (Aume an AC groun at the emitter). 2 - Repeat for a ifferent ivier reitane. 3 - Set up the iruit an ue the igital meter to meaure the voltage peifie in tep an 2. An emitter ypa apaitor i not neee for thee DC meaurement.

8 2-3. p = 20, = 2, DSS = 8 ma, = 0K 4-7. p = 20, n = -20, = 0K 8-0. p = 20, n = -20, = 0K, R = 20K, h fe = R 2 = 4.7K 9. R 2 = 50K -3. p = 25, R = 3.3K, = 20K, h fe = 00. R 2 = 3.9K R 4 = 20K 2. R 2 = 33K R 4 = 50K