ec laboratory objectives : design, simulation and...

EC laboratory

Objectives :

Design, Simulation and Breadboard implementation of relatively simple analog circuits.

Diagnosing and fixing faults in the circuit.

G-NumberB. Mazhari, IITK1

Experiments

Experiment No.

Experiment Name No. of Labs required

1 Parameter extraction for diodes and Transistors

2

2 Measurement of opamp parameters and design of an Integrator

1

3 Design of a CE amplifier 14 Design of a Schmitt Trigger

O ill1

Oscillator5 Design of a Diff. pair-emitter

f ll lifi i it1

follower amplifier circuit6 Design of a opamp based wave

shaping circuit1

G-NumberB. Mazhari, IITK2

shaping circuit

Design Process

SPECS.

Simplified Device

RapidPrototyping

Circuit

Design Processp

Model Prototype

MeasurementSchematic

Circuit Device Measured

MeasurementProcess

Simulation

Predicted

Model Results

SpecsNo Results Specs.

Satisfied?

Yes No Specs.

Satisfied?Fabrication

Process

G-NumberB. Mazhari, IITK3

Yes

DESIGN

Pre-Lab.

ANALYSIS of RESULTS SIMULATION

Post -Lab.

BREADBOARD IMPLEMENTATIONMEASUREMENT

G-NumberB. Mazhari, IITK4

In -Lab.

Lab. Report: 3 sections

Pre-Lab write-up:

Design procedure Circuit diagrams with values of all the components Circuit diagrams with values of all the components Circuit Simulation results

In Lab write up:In-Lab write-up:

Measurements made during the Lab Measurements made during the Lab.

Any design modifications carried out in light ofG-NumberB. Mazhari, IITK

5

Any design modifications carried out in light ofthe measurements made.

Lab. Report

Post-Lab write-up

Analysis of measurement made during the lab.

Comparison of experimental results with simulation ltresults

G-NumberB. Mazhari, IITK6

EE380: EC LabEE380: EC Lab

Exp. 1 : Parameter Extractionfor Diode & BJT

B. MazhariDept. of EE, IIT Kanpur

G-NumberB. Mazhari, IITK7

SPECS.

Design ProcessSimplified Device

Model

CircuitSchematic

CircuitSimulation

DeviceModel

PredictedResults

No Specs. )1( T

D

nVV

eIISatisfied?

Yes

)1( TSo eII

G-NumberB. Mazhari, IITK8

Yes

Objective

Measure parameters of a PN junction Diodep j

Measure parameters of a Bipolar Junction p pTransistor (BJT)

C t i t E i t il bl CRO F tiConstraints: Equipment available: CRO, Functiongenerator, power supplies; variety of

i d ti tpassive and active components.

N A t it t !G-NumberB. Mazhari, IITK

9

No Ammeter or capacitance meter!

Larger objective: understand methodology and problems associated with measurement of model parameters in general.

( ; )y f x x x p p p 1 2 1 2( , ,... ; , ,... )n ny f x x x p p p

-Select pm and find a set of {xi} such that y depends only on pm.

-Select pk and find a set of {xi} such that y depends only on pk and pm.

G-NumberB. Mazhari, IITK10

Example - I

R

C I

VIN(t)

);( CRVfI G-NumberB. Mazhari, IITK

11

),;( CRVfI IN

Measure R first

R

C

RI

VININ

RVRVfI /);( G-NumberB. Mazhari, IITK

12

RVRVfI inIN /);(

Extract C Next

R

C

RI

VIN(t)IN( )

)(tan; 1

2RCVI ino

G-NumberB. Mazhari, IITK13

)(1 2RC

Example - 2

R C

I

R C

VIN(t)

),;( CRVfI IN

G-NumberB. Mazhari, IITK14

V (t)VIN(t)

VINO

ti(t)

VINO/R

= RC

t

G-NumberB. Mazhari, IITK15

Diode Model

CJ

IO= ID

CD

C

dtdI

dtdVCII oD

joD )1( T

D

nVV

So eII m

j

D

joj

VV

CC

)1(

G-NumberB. Mazhari, IITK16

dtdt j

IS : Reverse Saturation CurrentSN : Ideality FactorCJO : Junction Capacitance at zero biasV J ti P t ti lVJ : Junction PotentialM : Grading Coefficient : Transit time : Transit time

The parameters of the model have to be measured bydesigning suitable experimentsdesigning suitable experiments.

Each experiment is a system of constraints that isp yimposed on the device so that only one parametermanifests itself.

G-NumberB. Mazhari, IITK17

Parameter IS

dIdVCII oDjoD )1( T

D

nVV

eIIdtdtjoD )1( TSo eII

It can be measured by imposing the following constraints

Use dc measurements to eliminate time dependent terms

Suitable plotting of measured IO vs. VD data.

G-NumberB. Mazhari, IITK18

Measurement of IO vs. VD characteristics

The measurements have to be done with theinstruments available in the lab which include anoscilloscope, a function generator and powersupplies.pp

(An ammeter is not available)( )

VO

VIN R

G-NumberB. Mazhari, IITK19

By measuring VO, we know diode current directly Oand we obtain diode voltage through the difference (VIN – VO).

Example: V = 5V and V = 4 34V so that V = 0 66VExample: VIN = 5V and VO = 4.34V so that VD = 0.66V.

Problems: VD is sensitive to measurement errors !

1% error implies VIN = 5.05V and VO = 4.29 and V = 0 76 which represents error of 15%VD = 0.76 which represents error of 15%

G-NumberB. Mazhari, IITK20

Avoid obtaining an estimate of a variable which is thedifference of two quantities which are very close in valueq y

yxz yxz y

yy

yxx

xz

yxzz

yxy

z yxxx

VO

VIN R

G-NumberB. Mazhari, IITK21

Better Measurement Procedure

RVO

VIN

RVVI Oin

O

R

Diode voltage can be obtained directlyDiode voltage can be obtained directly.

A 1% error results in only 1.3% error in current !

G-NumberB. Mazhari, IITK22

A 1% error results in only 1.3% error in current !

Opamp based Circuit

yxzz

yxz yxxx yxz

Error is least when y ~ 0

R

VD

R

VIN

VD

G-NumberB. Mazhari, IITK23

( 1) ln( ) ln( )D

T

VnV DVI I e I I ( 1) ln( ) ln( )T

o S o ST

I I e I InV

1E-3

1E-4

t (A

)

Slope n

1E-5

de C

urre

nt

Intercept I1E-6D

iod Intercept IS

0.45 0.50 0.55 0.60 0.65 0.701E-7

Di d V lt (V)

G-NumberB. Mazhari, IITK24

Diode Voltage (V)

Current Range

Since the data taken will eventually be plotted on a semi-loggraph and diode voltage changes relatively slowly withcurrent it is important that current be measured over severalcurrent, it is important that current be measured over severalorders of magnitude.

(This is why a variable resistor has been chosen for varying(This is why a variable resistor has been chosen for varyingthe current instead of voltage)

Diode Current(mA)

Diode voltage(mV)(mA) (mV)

5 659.240 5 590 23 V

R

0.5 590.230.05 521.79

VIN

VD

G-NumberB. Mazhari, IITK25

0.005 452.77

Junction Capacitance Parametersjo

j

CC

dm

j

Dj

VV

)1( dtdI

dtdV

CII oDjoD

IS : Reverse Saturation CurrentN : Ideality FactorCJO : Junction Capacitance at zero biasV : Junction PotentialVJ : Junction PotentialM : Grading Coefficient : Transit time : Transit time

Each experiment is a system of constraints that isimposed on the device so that only one parameter

G-NumberB. Mazhari, IITK26

imposed on the device so that only one parametermanifests itself.

Simple Capacitance Measurement Method

dtdvCi in )sin( tvv inoin

( ) ( )o inoi i Cos t C v Cos t /o inoi v Co ino

R

C

RF

VOFoo Rvi

G-NumberB. Mazhari, IITK27

Junction Capacitance is bias dependence

D

joj V

CC

)1(

m

j

D

V)1(

Diode Voltage (VD) Capacitance CJg ( D) p J

0 CJO0 CJO

-12-2

-4

G-NumberB. Mazhari, IITK28

Magnitude and frequency of sinusoidal voltage?

RF

CJ

jC

VO

m

D

joj

VV

CC

)1(

VR

jV

Voltage applied for measurement v should be smallG-NumberB. Mazhari, IITK

29

Voltage applied for measurement vin should be small

10o ino j Fv v C R mV

C 40 pF 74 10v R f CJ ~ 40 pF 4 10ino Fv R f

Vino ~ 0.1V8104fRF

The frequency should be below the unity gain frequency of theopamp (for 741 opamp, fT = 1MHz).

A frequency of 100KHz and RF = 10K should workA frequency of 100KHz and RF = 10K should worksatisfactorily.

G-NumberB. Mazhari, IITK30

Make sure that there is 900 phase shift between i/p and o/p

Transit Time

dtdI

dtdVCII oD

joD dtdtj

VO(t) IFR

VIN(t) R

tVF

V

-IRR

RRVR

l (1 )FI

G-NumberB. Mazhari, IITK31

ln(1 )FRR

RI

Input Waveform

To forward bias the diode at a current of few mA we chooseVF = 5V and R=1K.

Although the expression we shall use for transit timemeasurements works well when IF/IR = 0.1, experimentally itF R , p yis much more convenient to measure it for IF/IR ~1. For thatVR = -5V is chosen.

G-NumberB. Mazhari, IITK32

BJT Parameters

V 2 5

T

BEVV

A

CESC e

VVII )1( 2.0

2.5

)A

1.0

1.5

I C (m

AF

FB

II

0.0

0.5

F 0.0 0.2 0.4 0.6 0.8 1.0VCE(V)

Display IC vs. VCE Characteristics on CRO for a fixedIB.

G-NumberB. Mazhari, IITK33

B

Circuit Diagram

VIN (CRO X)

R

RC

RF

IRB VOIE (CRO Y)RB

VVB

G-NumberB. Mazhari, IITK34Assumption IC ~ IE

10

6

8

4

6O(V

)

2

-VO

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

VCE(V)

G-NumberB. Mazhari, IITK35

Need to understand the nature of waveforms to debug design

2.5

VIN (CRO X)

1.0

1.5

2.0

2.5

C (m

A)RF

RC

V0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.5

I C

VCE(V)

VOIE (CRO Y)RB

VB

81012

V CE V IN

V O

2468 O

(V)

4-202

Vol

tage

-8-6-4V

G-NumberB. Mazhari, IITK36

0.0 0.5 1.0 1.5 2.0-10

Tim e(m s)

Measurement of VA

T

BEVV

CESC eVII )1(

ASC e

VII )1(

IC

G-NumberB. Mazhari, IITK37

VCE-VA

Measurement small signal output resistance rO

CAIC

CEo IV

IV

rB

CI

c

ceo i

vr c

G-NumberB. Mazhari, IITK38

Circuit Diagram

VCC

vRC

c

ceo i

vr

VINRF

VRB VORB

RLVVB

G-NumberB. Mazhari, IITK39