İzmir University of Economics

EEE 331 Analog Electronics

1-1

LO-1

DC and AC Small Signal Analysis of Wide Band Transistor Amplifiers

Common Source Amplifiers 1. For the NMOS common-source amplifier given in the following figure.

(a) Determine the quiescent point values of ID and VDS. (b) Find the AC small-signal voltage gain. (c) Determine the maximum symmetrical swing in the output voltage.

The circuit parameters VDD = 12 V, RS = 2 k, RD = 3 k,

R1 = 300 k R2 = 200 k

RL = 3 k

The transistor parameters VTN = 2 V,

KN = 1 mA/V2, = 0.

2. Repeat the Problem 1 if the source resistor is bypassed by a source capacitor CS.

3. Consider the NMOS common-source amplifier given below.

The circuit parameters V+ = 5 V, V- = -5 V,

RD = 10 k, RL = 10 k

The transistor parameters

VTN = 1 V, KN = 0.5 mA/V2, = 0.01 V-1

(a) Determine IDQ to achieve the maximum symmetrical swing in the output voltage. (b) Find the AC small signal voltage gain.

1-2

4. For the common-amplifier given below, to minimize the loading effects, the drain resistance should be RD 0.1 RL.

(a) Determine IQ such that the Q-point is in the center of the saturation region. (b) Determine the open-circuit (RL = ) AC small-signal voltage gain. (c) By what percentage does the AC small-signal voltage gain decrease when RL is

connected.

The circuit parameters RL = 20 k

The transistor parameters

VTP = -1.5 V, KP = 2 mA/V2, = 0.01 V-1

5. For the common source amplifier given below,

(a) Determine RD and RS such that IDQ = 2 mA and VDSQ = 6 V. (b) Determine the AC small signal voltage gain. (c) If vi = Vi sint, determine the maximum value of Vi such that vo is an undistorted sine

wave.

The circuit parameters VDD = 10 V, RL = 2 k

The transistor parameters

VTN = -1 V, KN = 4 mA/V2,

= 0.

Common Drain (Source Follower) Amplifiers

6. Consider the source follower circuit given below, if IQ = 1 mA, (a) Calculate VDSQ. (b) Determine the AC small signal voltage gain Av = vo/vi. (c) Determine the output resistance Ro.

1-3

The circuit parameters VDD = 5 V, VSS = -5 V,

RG = 500 k, RL = 4 k

The transistor parameters

VTN = 1.2 V, KN = 1 mA/V2, = 0.01 V-1

7. For the source follower amplifier given below,

(a) Calculate IDQ and VSDQ. (b) Determine the AC small signal gains Av = vo/vi and Ai = io/ii. (c) Determine the output resistance Ro.

The circuit parameters VDD = 10 V, RS = 4 k,

R1 = 1.24 M R2 = 396 k

RL = 4 k

The transistor parameters VTP = -2 V,

KP = 2 mA/V2, = 0.02 V-1

8. Consider the source follower amplifier given below. The circuit and transistor parameters

are listed. (a) Design the circuit such that

IDQ = 0.25 mA and VDSQ = 1.5 V. (b) Determine the AC small signal voltage

gain. (c) Determine the output resistance Ro. The circuit parameters VDD = 3 V, Ri = 300 k, The transistor parameters VTN = 0.4 V, KN = 0.5 mA/V2 = 0

1-4

9. Consider the source follower with a depletion NMOS given below. The most negative output signal voltage occurs when the transistor is just cuts off. Show that this output voltage vo(min) is given by

LS

DQ

oRR

RIv

1

-(min)

2

Show that the corresponding input voltage is given by

LSm

m

DQ

i RRgg

Iv //(1(min)

Common Gate Amplifiers

10. For the common gate amplifier given below, (a) Calculate IDQ and VDSQ. (b) Determine gm and ro. (c) Find the AC small signal voltage gain Av = vo/vi. (d) Determine the output resistance Ro.

The NMOS parameters

VTN = 1 V, KN = 3 mA/V2,

= 0

11. For the source follower amplifier given below,

The PMOS parameters

VTP = -1 V, KP = 0.5 mA/V2,

= 0

(a) Determine RS and RD such that IDQ = 0.75 mA and VSDQ = 6 V. (b) Determine the input resistance Ri and the output resistance Ro. (c) Determine the load current io and the output voltage vo, if ii = 5 sin t A.

1-5

12. For the common gate amplifier given below, (a) Find RD such that IQ = 5 mA and VDSQ = 12 V. (b) Calculate gm and Ri. (c) Determine the AC small signal voltage gain Av = vo/vi.

The circuit parameters V+ = +10 V V- = -10 V

RG = 100 k, RSi = 0

RL = 2 k

The NMOS parameters VTN = 2 V,

KN = 4 mA/V2, = 0

Amplifiers with MOSFET Load

13. Consider the NMOS amplifier with saturated load as given below. (a) Design the circuit such that the AC small

signal voltage gain is |Av| = 5 and Q-point is in the center of the stauration region.

(b) Determine IDQ and the dc value of vO.

The circuit parameters VDD = 10 V, The transistor parameters VTND = VTNL = 2 V,

(W/L)L = 0.5 D= L= 0.

14. A source follower circuit with a saturated load is shown in the figure below. (a) Determine VGG such that the quiescent value

of vDSL is 4 V. (b) Show that the AC small signal open circuit

(RL = ) voltage gain about this Q-point is

given

(c) Calculate the small-signal voltage gain for RL = 4 k.

The circuit parameters VDD = 9 V The transistor parameters VTND = VTNL = 1 V, KND = 1 mA/V2, KNL = 0.1 mA/V2 D= L= 0.

1-6

15. The ac small-signal equivalent circuit of a CMOS common source amplifier is shown below. Determine the small-signal voltage gain

The circuit parameters VDD = 9 V, The NMOS transistor parameters (M1) VTN = 0.5 V

(W/L)1 = 50 = 0.05 V-1 The PMOS transistor parameters (M2 & M3) VTP = -0.5 V

(W/L)2,3 = 50 = 0.075 V-1

16. Consider the ac small-signal equivalent circuit of a CMOS common source amplifier given

below. Determine the small-signal voltage gain

The circuit parameters VDD = 9 V, The PMOS transistor parameters (M1) VTP = -0.5 V

(W/L)2,3 = 50 = 0.075 V-1 The NMOS transistor parameters (M2 & M3) VTN = 0.5 V

(W/L)1 = 50 = 0.05 V-1

1-7

Multistage Amplifiers

17. Consider the multistage amplifier given below. (a) Design the circuit such that IDQ1 = 0.2 mA and IDQ1 = 0.5 mA. (b) Determine the resulting values of VDSQ1, and VDSQ2. (c) Calculate the resulting voltage ac small-signal voltage gain Av = vo/vi. (d) Determine the input resistance Ri and the output resistance Ro.

The transistor parameters VTN1 = VTN2 = 1 V KN1 = 500 A/V2 KN2 = 200 A/V2

= = 0.

18. Consider the multistage amplifier given below.

(a) Determine IDQ1, IDQ2, VDSQ1, and VDSQ2. (b) Determine gm1 and gm2. (c) Determine the overall ac small-signal voltage gain Av = vo/vi.

The transistor parameters VTN1 = 1 V VTN2 = 1 V KN1 = 4 mA/V2 KN2 = 4 mA/V2

= = 0.