Download 100-1007 No Tempco VCO

100-1007 No Tempco VCO
1. Theory Of Operation.
The VCO uses a purely electronic means of compensating for the scale drift in
exponential transistor pair. This is not a new concept. The Curtis CEM3340 VCO did
this some twenty years ago. But, that part is no longer being made. So, coming up with a
way to do this was not an easy thing to do. In fact, I have been trying to do it ever since
the CEM3340 first came out simply because it was a puzzle to solve. It wasn’t until
1998, however, that I really started working on this problem in earnest. And, there were
a few false starts, but it would seem I now have a circuit that does this job fairly nicely.
While this does a considerable complexity to the circuit, it does not cost a whole lot,
compared to the solution using a temperature compensating resistor. Those resistors can
cost between $5 to $10 each. There are less expensive parts, however, they don’t have
the exact temperature dependence needed. There are ways to get around all this, but
some of the solutions are not very satisfactory.
Looking at the schematic, U9A and U9B make up the gain control element that
controls the temperature coefficient of the voltage applied to the base of Q6A (pin 2).
The LM13700 connect in this fashion does two things. First the Tempco of U9A is
canceled out by the Tempco of U9B, and second, the non linearity’s of the two amplifiers
also cancel each other out. The overall linearity is about 0.1%.
The transfer function for this combination is:
VO = R47 * gmU9B * VIN / (gmU9A * R44 + 1)
(1)
GmU9A will nominally be 0.0081 mhos.
The current that controls GmU9B is a bit more problematic. Q6C and the reference
leg of Q6A (Pins 3,4,5) form a band gap reference. The output voltage will be
proportional to absolute temperature. For room temp it should be:
VBG = VT * ln(500); VT = 0.026V @ room temp (2)
The 500 value is the ration of the two currents, which is set by the ration of
R43/R101 = 500. The amplifier supplying the current has a gain of 10. So, IABC2 will
be:
IABC2 = 10 * VBG / R57 = 10 * 0.1616 / 4.02K
(3)
So IABC2 will be about 0.4 mA.
This will make GMU9B nominally 0.0077 mhos. So, substituting all of this into
the above equation (1) we get:
VO = 0.01905 * VIN
(4)
So, as you can see, we will get about 19mV/V at the base of Q6A (Pin 2), which
is a bit high perhaps, but that is what the pot is for.
IABC2 will vary with temperature, because, that is what it is supposed to do,
always adjusting the gain of the VCA so that the scale factor will remain constant with
temperature.
Q6B is used to generate a current that can be used to correct for the bulk
resistance of the exponential transistors. The collector of Q6B is fed into an opamp that
converts the current to voltage. R39 then allows you to adjust the amount of voltage that
gets fed back into the converter. This seems to be a very clean way of generating this
signal. We don’t need to worry about offsets added by the usual method of using the
output of the reference leg servo amp.
The oscillator itself is just a standard sawtooth oscillator that has been around for
a long time. You will find this oscillator in past issues of Electronotes. The circuit is
one that was done by Terry Michaels. It is also sometimes referred to as the ASM-1
oscillator. The sawtooth output of the oscillator then goes into wave shapers that are
pretty much standard. I did add a divider that will produce divide by 2,3, and 4 ratios.
II. Construction
You should note the following changes.
For the REV N.C. board, the silkscreen reads wrong for the following parts.
Reference Designator
R47
R57
R58
Silkscreen Reads
200
11.3K
10K
The value should be
1K
4.02K
11.3K
The only part you may have difficulty finding is the CA3280. All of the other
parts should be commonly available. Most can be purchased from either Digikey or
Mouser.
5
4
3
2
1
R1
VCOCORE
JP2
1
3
5
7
9
11
13
15
17
19
21
23
25
D
PVPV+
FC0
FC1
FC2
FC3
FC4
SYNC
PWCV0
PWCV1
PWCV2
PWCV3
LINFM
2
4
6
8
10
12
14
16
18
20
22
24
26
JP1
WAVESHAPERS
VC0
VC1
VC2
VC3
VC4
SYNC
VREF5P
VREF5N
LINFM
SAWOUT
SAWIN
PWMCV1
PWMCV2
PWMCV3
PWMCV4
1K
2
4
6
8
10
12
14
16
TRI
PWM
DIV2
DIV4
DIV3
SIN
VR5P
VR5N
1
3
5
7
9
11
13
15
D
HEADER 8X2
WAVESHAPERS
SIMPLEVCO
+10R
-10R
HEADER 13X2
+10R
+15
+15
R3
R4
3 +
C
R5
100K
4.99K
20K
C
R6
1
2 -
R7
10K
U1A
2 -
-10R
TL052
4
MISC
U3A
8
8
R2
100K
15K
1
3 +
SAW OFFSET
4
TL052
-15
-15
-10R
U2B
R9
R8
100K
misc
5 +
U3B
6 -
10K
5 +
R11
100K
7
TL052
R10
7
6 -
10K
R12
TL052
10K
B
B
R13
15K
R14
10K
FREQUENCY
POT SCALE
R15
JP3
+15
1
2
3
4
+15
8
-15
10K
U2A
HEADER 4
R16
2 -
1
3 +
TL052
4
10K
R17
A
10K
A
-15
Title
TEMPERATURE COMPENSATED VCO
Size
Document Number
Rev
NC
100-1007
Date:
5
4
3
2
Saturday, March 01, 2003
Sheet
1
1
of
4
5
4
3
2
+15
+15
+15
1
+15
+15
+15
+15
R18
10K
C1
.1uF
C2
.1uF
C3
.1uF
C4
.1uF
C5
.1uF
C6
.1uF
+15
-15
U4B
D
R19
100K
-15
-15
D
Q1
2N3904
7
6 1K
TL052
2
-15
R20
5 +
C7
.1uF
Q2
U5
C8
.1uF
C9
.1uF
C10
.1uF
2N3904
R21
20K
1
R22
10
+15
+15
+15
+15
+15
+15
3
LM4041CZ-ADJ
R24
R23
100K
+10R
R25
10K
C36
.1uF
30K
+
-15
+
C
C37
.1uF
C38
.1uF
C39
.1uF
C42
.1uF
C43
.1uF
C11
10uF
-15
-15
-15
-15
-15
C12
10uF
C44
.1uF
R26
C45
.1uF
C46
.1uF
C49
.1uF
C50
.1uF
C51
.1uF
C
-10R
100K
R27
10
8
+15
R28
2N3906
U4A
R29
2 24.9K
Q3
Q4
2N3906
1
3 +
1K
4
TL052
-15
-15
B
B
A
A
Title
POWER SUPPLY/REFERENCES
Size
Document Number
Rev
A
100-1007
Date:
5
4
3
2
Tuesday, January 14, 2003
Sheet
1
2
of
4
5
4
3
REVISION HISTORY
10-18-2002 REMOVED BOGUS TEMP COMP CIRCUIT
AND REPLACED WITH ONE THAT WORKS
2
Q5
J111
2-1-2003 Changed temp sensor on advice from Scott
Bernardi. Added reference transistor to remove
effects from Is. This seems to have cured the
mysterious 400ppM drift I still had.
+15
C16
C17
+15
.0022uF
SYNC
2
-
3
+
C13
.1uF
-15
C14
.1uF
C15
.1uF
6
TL071
2
+
3
-
10K
C19
.1uF
7
-15
-15
-15
D
C20
.1uF
C21
.1uF
C22
.1uF
C23
.1uF
R32
3.3K
4
1
4
8
1
LM311
100K
-15
U7
5
6
8
R31
.01uF
R33
VC0
10K
-15
100K
R35
-15
SAWOUT
Terry Michaels Oscilator
VC1
100K
R36
R37
R38
VC2
R39
100K
R40
C
+15
18pF
R30
100
U6
7
5
C18
+15
+15
D
R34
1
20K
TRACKING
1M
R41
10K
U8B
VC3
6 100K
R42
100K
+15
C
7
5 +
+15
VC4
TL052
Tracking
R44
2 -
U9A
1
13
100pF
U10B
Q6A
4
Q6C
3
lm13700
TL052
S
CA3046
C25
1
-15
R47
1K
7
5 +
9
10
Q6D
+
6 -
12
-15
3
CA3046
11
14
5
13
2
5
CA3046
Q6B
2
-
7
4
CA3046
6
U9B
+
16
14
6
4
R45
1K
C24
.001uF
R48
4.99K
VREF5P
R102
10K
+15
Temp Reference
100pF
R49
20K
OFFSET
8
B
R101
10K
12
49.9K
1
15
TL052
R46
1M
R43
4.99M
lm13700
-
8
3 +
11
8
C56
U8A
R50
2 -
VREF5N
10M
R103
B
U10A
1
3 +
4
TL052
1M
+15
-15
U11B
R52
R104 100K
1K
8
SCALE
C26
.01uF
U11A
6 R54
3 +
R53
2N3906
Q8
2 -
100K R105
Exponential Servo
Q7
7
5 +
1
2N3906
LM358A
1K
R106
4
LM358A 1K
1M
R56
9.09K
Scall Control
Band Gap
Temp
R57
4.02K
R58
11.3K
-15
A
A
LINFM
Title
Simple Temp Compensated VCO
Size
Document Number
Rev
A
100-1007
Date:
5
4
3
2
Sunday, April 27, 2003
Sheet
1
3
of
4
5
4
3
2
1
R59
TRI
PWM
DIV2
DIV3
DIV4
R60
R61
10K
R62
1K
R63
1K
+15
10K
5
Q
R67
K
Q
8
12
8
Q
D
15
CLK
11
4027
D6
U13B
9
16
2
VDD
7
S
13
CLK
K
J
9
Sawtooth to Triangle Converter
10
S
1K
TL052
4
TL052
1
R
10K
3
U13A
Q
VSS
7
5 +
J
16
10K
6
R
1
1N914
R66
6 -
3 +
D5
U12B
R65
16
1N914
VDD
2 -
SAWIN
39K
D2
1N914
VSS
8
U12A
4
D1
R64
D
14
4027
1N914
20K
-15
R68
PWMCV1
R70
-10R
R71
2 -
PWMCV4
6 -
R79
1
3 +
100K
R77
S
VDD
S
4.99K
Q
15
CLK
11
K
4027
14
4027
C
R78
7
5 +
100K
TL052
TL052
1K
1K
100K
4
Q
2
U14B
Q
12
U15B
R76
K
J
13
CLK
8
8
U15A
10
R
5
100K
R75
C
3
Q
VSS
R107
100K
+15
PWMCV3
J
1K
1
8
100K
R74
R
6
U14A
7
16
68K
VDD
R69
20K
R73
VSS
PWMCV2
4
100K
R72
D3
Pulse Width Modulator
+15
1N751
-15
C52
.1uF
D4
C53
.1uF
C54
.1uF
C55
.1uF
R80
10
1N751
C28
10uF
+
+15
R81 100K
8
R99
50K
SINE DISTORTION
V+
4
+ C30
C32
10uF
13
Iabc
+15
+15
R89
100K
-15
-15
2
3
-15
-
U17
R90
6
SIN
-15
+
100
R91
100K
4
8
1
TL071
R92
49.9
U18B
-15
6 -
+15
11
10uF
CA3280E
+
O
-
12
A
Id
E
Iabc
10
C35
V+
9
R96
A
R93
10
+
U16B
7
TL052
200
R95
20K
100pF
C34
5 +
VR5N
R94
+10R
B
R86 10uF
10
100pF
7
5
R85
2K
R83
10
TL052
3
R88
6.8M
V-
-
C29
100pF
1
C31
O
1
2
R87
1M
VR5P
CA3280E
+
Id
E
15
2 U18A
3 +
10K
+
B
4
16
14
U16A
R100 100K
C33
.1uF
R84
R82
30K
R97
100K
6
8
7
1M
R98
2K
-10R
-15
+15
Title
VCO-WAVESHAPERS/DIVIDERS
Size
Document Number
Rev
NC
100-1007
Date:
5
4
3
2
Sunday, February 02, 2003
Sheet
1
4
of
4
C:\projects\SynthMod\100-1007\100-1007.bom
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:
48:
49:
50:
51:
52:
53:
54:
55:
56:
57:
58:
59:
60:
61:
62:
63:
64:
65:
66:
67:
68:
69:
70:
71:
72:
73:
TEMPERATURE COMPENSATED VCO Revised: Saturday, March 01, 2003
100-1007
Revision: NC
Bill Of Materials
April 27,2003
12:53:25
Page1
Item
Quantity
Reference
Part
PART NO
______________________________________________
1
34
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
6
1
1
2
1
4
1
1
4
2
1
1
1
2
4
1
1
13
20
27
21
22
23
24
25
3
2
2
2
18
26
27
28
29
30
31
32
5
6
2
1
2
1
6
33
34
35
36
37
38
39
40
41
42
43
44
1
1
1
1
1
1
1
1
1
2
1
1
C1,C2,C3,C4,C5,C6,C7,C8,
.1uF
80-C410C104M5U
C9,C10,C13,C14,C15,C19,
C20,C21,C22,C23,C36,C37,
C38,C39,C42,C43,C44,C45,
C46,C49,C50,C51,C52,C53,
C54,C55
C11,C12,C28,C30,C32,C35 10uF
140-XRL35V10
C16 .0022uF 23PS310
C17 18pF
140-50N2-180J
C18,C26 .01uF
140-PF2A103J
C24 .001uF 140-PF2A102J
C25,C29,C31,C34 100pF
140-50P2-101K
C33 .1uF
140-PF2A104J
C56 100pF
D1,D2,D5,D6 1N914
625-1N914
D4,D3
1N751
610-1N752A
JP1 HEADER 8X2 571-1033113
JP2 HEADER 13X2 571-1033116
JP3 HEADER 4
Q1,Q2
2N3904 512-2N3904
Q3,Q4,Q7,Q8 2N3906 512-2N3906
Q5 J111
J111
Q6 CA3046
R1,R20,R29,R45,R47,R53, 1K 271-1K
R54,R60,R61,R66,R71,R77,
R78
R2,R5,R8,R11,R19,R23,R26,
100K
271-100K
R34,R35,R36,R40,R41,R42,
R68,R72,R73,R74,R75,R76,
R79,R81,R89,R91,R97,R100,
R104,R105
R3,R48,R107 4.99K
271-4.99K
R67,R4 20K 271-20K
R6,R14 10K 594-43P103
R13,R7 15K 271-15K
R9,R10,R12,R15,R16,R17, 10K 271-10K
R18,R25,R31,R33,R38,R59,
R62,R64,R65,R84,R101,
R102
R21,R39,R49,R69,R95 20K 594-43P203
R22,R27,R80,R83,R86,R93 10 271-10
R82,R24 30K 271-30K
R28 24.9K
271-24.9K
R90,R30 100 271-100
R32 3.3K
271-3.3K
R37,R46,R87,R96,R103,
1M 271-1M
R106
R43 4.99M
4.99M
R44 49.9K
271-49.9K
R50 10M
R52 1K 594-43P102
R56 9.09K
271-9.09K
R57 4.02K
271-4.02K
R58 11.3K
271-11.3K
R63 39K 271-39K
R70 68K 271-68K
R98,R85 2K 271-2K
R88 6.8M
R92 49.9
271-49.9
1
C:\projects\SynthMod\100-1007\100-1007.bom
74:
75:
76:
77:
78:
79:
80:
81:
82:
83:
84:
85:
86:
87:
45
46
47
48
49
50
51
52
53
54
55
56
57
1
1
5
1
1
1
1
1
1
3
2
1
1
R94 200 594-43P201
R99 50K 594-43P503
U1,U2,U3,U4,U8 TL052
595-TL052CP
U5 LM4041CZ-ADJ
511-LM336Z
U6 TL071
511-TL071
U7 LM311
511-LM311
U9 lm13700 LM13700N
U10 TL052
U11 LM358A 511-LM358AN
U12,U15,U18 TL052
595-TL052CN
U13,U14 4027
511-4027
U16 CA3280E
U17 TL071
511-TL071CN
2