User manual
page 40
Analog System Lab Kit PRO
experiment 6
To understand a classic mixed mode circuit that uses two-bit A to D Converter
along with an analog integrator block. The architecture of the circuit is similar
to that of a sigma delta converter.
The feedback loop is made up of a two-bit A/D converter (at
1
1
V
fRCRR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
fRCRR
kHz
RC
RR
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
21
1
2
1
2
21
ss
r
c
VCO
c
r
c
VCO
c
21
!
$
$$$
$
$
$
#
=
== =
=
=
l
l
__
__
_
ii
ii
i
levels), also
called Schmitt trigger, and an integrator. The circuit is also known as a function
generator and is shown in Figure 6.1. The output of the function generator is
shown in Figure 6.2.
The function generator produces a square wave at the Schmitt Trigger output and
a triangular wave at the integrator output with the frequency of oscillation equal
to
1
1
V
fRCRR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
fRCRR
kHz
RC
RR
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
21
1
2
1
2
21
ss
r
c
VCO
c
r
c
VCO
c
21
!
$
$$$
$
$
$
#
=
== =
=
=
l
l
__
__
_
ii
ii
i
. The function generator circuit can be converted as a linear
VCO by using the multiplier integrator combination as shown in Figure 6.3.
6.1 Brief theory and motivation
6.2Specications
6.3 Measurements to be taken
Goal of the experiment
1
1
V
f RC RR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
f RC RR
kHz
RC
R R
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
2 1
1
2
1
2
2 1
ss
r
c
VCO
c
r
c
VCO
c
2 1
!
$
$ $$
$
$
$
#
=
= = =
=
=
l
l
_ _
_ _
_
i i
i i
i
1
1
V
f RC RR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
f RC RR
kHz
RC
R R
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
2 1
1
2
1
2
2 1
ss
r
c
VCO
c
r
c
VCO
c
2 1
!
$
$ $$
$
$
$
#
=
= = =
=
=
l
l
_ _
_ _
_
i i
i i
i
The frequency of oscillation of the VCO becomes
U1
U2
R2R1
U1•U2
10
+
VG
VF1
R
C
VF2
Figure 6.1: Function Generator
Sensitivity of the VCO is the important parameter and is given as
1
1
V
fRCRR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
fRCRR
kHz
RC
RR
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
21
1
2
1
2
21
ss
r
c
VCO
c
r
c
VCO
c
21
!
$
$$$
$
$
$
#
=
== =
=
=
l
l
__
__
_
ii
ii
i
, where it is
given as
(6.1)
where
1
1
V
fRCRR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
fRCRR
kHz
RC
RR
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
21
1
2
1
2
21
ss
r
c
VCO
c
r
c
VCO
c
21
!
$
$$$
$
$
$
#
=
== =
=
=
l
l
__
__
_
ii
ii
i
VCO is an important analog circuit as it is used in FSK/FM generation and constitutes
the modulator part of the MODEM. As a VCO, it can be used in Phase Locked Loop
(PLL). It is a basic building block forming sigma delta converter. It can also be used
asreferenceoscillatorforaClassDamplier.
Design of a function generator which can generate square and triangular wave for
a frequency of 1 kHz.
Determine the frequency of oscillations of square and triangular wave. Frequency of
oscillation should be equal to
1
1
V
fRCRR
f
RC VR
VR
K
dV
df
RC VV
R
Vc
f
Hz Volts
fRCRR
kHz
RC
RR
V
K
dV
df
V
kHz
kHz
14
4
4
14
1
4
1
10
21
1
2
1
2
21
ss
r
c
VCO
c
r
c
VCO
c
21
!
$
$$$
$
$
$
#
=
== =
=
=
l
l
__
__
_
ii
ii
i
. Convert the function generator into a
Voltage Controlled Oscillator (VCO) or FM/FSK generator also called “mod of modem.”
Figure 6.2: Function Generator Output