0195136047.pdf

394 TRANSISTOR AMPLIFIERS Thus, a biasing signal (current or voltage), in the absence of any other signals, places the transisto ...

8.2 BIASING THE FET 395 RC= 3 VCC 8 ICQ (8.1.1) RE= VCC 8 (ICQ+IBQ) = VCCβ 8 ( 1 +β)ICQ (8.1.2) Noting thatVB=VE+VBEin Figure 8. ...

396 TRANSISTOR AMPLIFIERS + − VG VDD R 1 R 2 G S D RS RD Figure 8.2.1Method of biasing the JFET. From Figure 8.2.1, applying the ...

8.2 BIASING THE FET 397 or RD= VDD−IDQRS−VP 2 IDQ = 3 (VDD− 2. 923 VP) 2 IDSS (8.2.12) Note that the source voltageVDDmust be la ...

398 TRANSISTOR AMPLIFIERS + − VG VDD R 1 R 2 G S D RS RD Figure 8.2.2Biasing ann-channel enhancement MOSFET. iD=K(vGS−VT)^2 (8.2 ...

8.3 BJT AMPLIFIERS 399 Noting the supply voltage to be 20 V and the drop across the transistor 10 V, about 10 V can be allowed f ...

400 TRANSISTOR AMPLIFIERS C B E CE CC + − VCC + − VL Ground iS + − vS RS R 2 R 1 CB RC RE RL iL v 1 AC source Amplified output a ...

8.3 BJT AMPLIFIERS 401 where Rin= [ total input resistance seen by source ] =RB ∥ ∥Ri= RBrπ RB+rπ (8.3.4) Voltage and current ga ...

402 TRANSISTOR AMPLIFIERS Common-Collector (CC) Configuration A common-collector (CC) amplifier is also known as an emitter foll ...

8.3 BJT AMPLIFIERS 403 Rin=RB‖Ri= RBRi RB+Ri (8.3.8) in which Ri=rπ+RW( 1 +gmrπ) (8.3.9) where RW=ro‖RE‖RL (8.3.10) The voltage ...

404 TRANSISTOR AMPLIFIERS C B E CE CC + − VCC + − vL Ground R 2 R 1 CB RC RE RL iL RS iS npn BJT + − vS Rin (a) AC source Output ...

8.4 FET AMPLIFIERS 405 On comparing the CE, CC, and CB configurations one can come up with the following observations: RiandRin ...

406 TRANSISTOR AMPLIFIERS R 1 R 2 RD RL (b) RS + − vS + − vGS + − vL gmvGS Output Input S GD iS ro iL Rin = R 1 ||R 2 Ri −∞ Grou ...

8.4 FET AMPLIFIERS 407 Rin=R 1 ‖R 2 = 300 ( 100 ) 400 =75 k Ai= Rin RL Av 1 = 75 3 (− 2 )=− 50 Common-Drain (CD) JFET Amplifier ...

408 TRANSISTOR AMPLIFIERS R 1 R 2 (b) RS + − vS + − vGS + − vL gmVGS Output Input S GD ro Rin = R 1 ||R 2 Ri − ∞ Ground RSS RL F ...

8.5 FREQUENCY RESPONSE OF AMPLIFIERS 409 RS + − iS v S + − vL RSS v 1 Input gmvGS ro RD RL + − vGS GDiL S Output (b) Figure 8.4. ...

410 TRANSISTOR AMPLIFIERS Magnitude Av 0 Magnitude of gain Av0 2 Midband W3dB Phase angle of gain Phase 0 Deterioration due to c ...

8.5 FREQUENCY RESPONSE OF AMPLIFIERS 411 R 1 R 2 Cs RD RL (a) RS + − vS + − vGS + − vL gm vGS Output voltage Input ac source S C ...

412 TRANSISTOR AMPLIFIERS RL 2 =RD+RL (8.5.10) RL 3 =RS+RG (8.5.11) The frequenciesωZ,ωL 1 ,ωL 2 , andωL 3 are known as break fr ...

8.5 FREQUENCY RESPONSE OF AMPLIFIERS 413 From Equations (8.5.7) and (8.5.8), CD= 1 RL 2 ωL 2 = 1 RL 2 ωL/ 10 = 10 1900 ( 200 π) ...