MULTISTAGE AMPLIFIER Cascaded Connection Output of one stage is connected to the input of another stage.

Amplifier 1Gain = AV1

Amplifier 2Gain = AV2

Overall gain AV = VO2 / Vin 1 = Av1 AV2

Cascaded BJT Amplifier

Draw the (i) Input and (ii) output voltage waveshape for different values of Vi (a) 25V (b) 1mV (c) X mV, where X is last two digits of your Roll No.

Cascaded FET Amplifier

AV1 = -gm1RD1

AV2 = -gm2RD2

Overall gain AV1AV2 = (-gm1RD1)(-gm2RD2)

Input Impedance Zin = RG1

Output Impedance ZO = RD2

Darlington Connection

Overall = 1 2

Two transistors are connected in such a way that emitter current of one is fed to the base of another, so that the overall current gain is the product of their individual current gains.It is also known as superbeta transistorIE1 = (1+ 1 ) IB1 IE2 = (1+ 2 ) IB2 IE2 = (1+ 2 ) (1+ 1 ) IB1IE2 2 1 IB1

2N999 npn darlington transistorVBE = 1.8V at IC = 100mAD = 4000 at IC = 10mA D = 7000 at IC = 100mAMaximum D = 70,000 at IC = 100mA

DC bias of Darlington CircuitVCC

DC bias of Darlington Circuit18VVBE = 1.6VD =8000

AC analysis of Darlington Circuit

AC Input Impedance of Darlington CircuitD =8000ri = 5K

AC Current Gain of Darlington Circuit

AC Output Impedance of Darlington Circuit

AC Voltage gain of Darlington Circuit

Summery of Darlington connectionSuper beta transistor, D = 1 2.High current gain, can amplify very small signal.Increased input impedance.Reduced output impedance.Unity voltage gain.

CMOS CircuitComplementary Metal Oxide Semiconductor Field Effect TransistorVi = 0VVo = 5VVDD = 5V Vi = 5VVo = 0VVDD = 5VCMOS is used as an inverter

Current sourceRL = 2RL = 2KVDD = 24V

BJT Current source

BJT - Zener Current source

Current Mirror Circuit