Question

Find the induction process of A, β, Ro, Ri.

EXAMPLE 10.10 Figure 10.27 shows a feedback current amplifier formed by cascading an inverting voltage amplifier u witha MOSFET Q. The output current I, is the drain current of Q. The feedback network, consisting of resistors R, and R, senses an exactly equal current, namely, the source current of Q, and provides feedback current signal that is mixed with I, at the input node. Note that the bias arrangement is not shown The amplifieru can be implemented in a variety of ways, including by means of an op amp, a differential amplifier, or a single-ended inverting amplifier. The simplest approach is to implement u with a CS MOSFET amplifier. However, in such a case the loop gain will be very limited. (the amplifier /u has an output resistance ro1 a input resistance Rd, open-circuit voltage gain , an EXAMPLE 10.10 (a) Roat Rof ww 3R R Figure 10.27 Circuit for Example 10.10.

Answer 1

When the loop in AR>j A * 1+ap USed to 2 The B ctcuft, shoon n tue ( doterimine B e (D. as shouon fn dfuf sfon R2 RR 2 Thus clealy,toe ohat hafpens we have assomed the looP so tat Io Coso moxe To see Here laxpe Aso note that and thus I be clase because I O, V -I R2 to teso Thus use can AN ltage at the detexmi ne the SOuxce as (Is The cnent theoghuil then be , e (-t R wch means tat the The souke cvwent d at bo hich conans the expessfonfoA abtaned obove n 2 RS yVP RI Uxe )

bac ampie simpy beuse t 2 the feebnck netucek fs opened). He aso load te astput the s (becaase post A coutt sshoon fo cad the pot 3ide the cacoft To abtain the A we asfh Ra and R, The laterîn Tfs case shosted) igode ed heee haue eplocel the amplfter yth T equualent the teedbnck netcark s taightfouad ard peioceeds cicutt. Aralysis f the A ctautt ts Rs RCR as Rt It Rf 4 To ) + Ril tRIR and esul in A: Comdbtntngstons RP A = (RllR.1 (RR (Rllrl A + Notng hat Ro fsthe autput eslstance at ,whteh has lead esistance a ute fin fts con uge Ro