ec laboratory objectives : design, simulation and...
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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