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tors. The output current range of the DAC normally reaches from 0
to -2mA. In this application, however, the current range is set
Voltage-Controlled Resistor (VCR)
through RREF (10k&!) to 0 to -1mA.
Because an OTA is capable of producing an output current propor-
tional to the input voltage, a voltage variable resistor can be made.
VREF 5V
Figure 6 shows how this is done. A voltage presented at the RX IDACMAX + 2 @ + 2 @ + 1mA
RREF 10k
terminals forces a voltage at the input. This voltage is multiplied by
gM and thereby forces a current through the RX terminals:
R ) RA
RX=
gM ) RA
INT
V
C
+V
CC
+V
CC
R I
1 ABC
R
3
4 = R2/ /R3
+
1
11
5
7
NE5517
R
2
6
8
V
IN
4 V
OUT
I R
OUT L
R
R
S
3
INT
-V
CC
TYPICAL VALUES: R
1 = 47k
R
2 = 10k
R
3 = 200&!
R
4 = 200&!
R
L = 100k
R
S = 47k
Figure 3.
August 31, 1994 100
Philips Semiconductors Linear Products Product specification
Dual operational transconductance amplifier NE5517/5517A
+V
CC
10k
3
+
V
11
IN1
INT
R
IN
15k
+V
CC
NE5517/A
R
P
R
1k
D
+V
CC
I
ABC 8
1
4
V
OUT1
R
L
10k
30k
V
C
5.1k
R
C
10k
14 16
+
V
-V
IN2
CC
I
R ABC
IN
15k
15
+V
10
CC
NE5517/A
R
P
1k R 12
+V D
CC
6 9
13
V
OUT2
R
L
10k
R
S
-V
CC
INT
Figure 4. Gain-Controlled Stereo Amplifier
R
C
30k
V
IN2
1
SIGNAL
I
ABC +V
CC
11
I INT
D
3 +V
CC
+
15k
2
5 7
NE5517/A
1k
V
OS
V
IN1
8
4
CARRIER
R
10k V
L
OUT
10k
R
S
6
-V
CC
-V
CC
INT
Figure 5. Amplitude Modulator
R ) RA
RX +
gM @RA
30k
+V
V
CC
C
INT
3 +V
11
CC
+
I
O
2
NE5517/A
5
7
C
4
8 V
OUT
R
X R
200 -V
200
CC
10k
100k
-V
CC
INT
Figure 6. VCR
August 31, 1994 101
Philips Semiconductors Linear Products Product specification
Dual operational transconductance amplifier NE5517/5517A
+V
CC 1 30k
V
C
+V
CC
I
D
INT
3 +V
11
CC
R
P
2
V
OS
NE5517/A
1k
5
7
C
6
4
8
R
X R
-V
CC
10k
100k
-V
CC
INT
Figure 7. VCR with Linearizing Diodes
1
30k
V
C
+V
CC
I
ABC
INT
100k
3 +V
11
CC
V
+
IN
2
NE5517/A
5
7
C
6
150pF 8
4
V
OUT
R
200
R 200 -V
CC
A 10k
100k
-V
CC
INT
NOTE:
RA gM
fO +
g(R ) RA) 2pC
Figure 8. Voltage-Controlled Low-Pass Filter
1
30k
V
C
+V
CC
+V
CC
I
ABC
INT
100k
V 3 +V
11
OS CC
+
NULL
2
NE5517/A
5
7
-V
CC
C
6
8
0.005F
4
V
OUT
R
A
R
1k -V
1k CC
10k
100k
-V
CC
INT
NOTE:
RA gM
fO +
g(R ) RA) 2pC
Figure 9. Voltage-Controlled High-Pass Filter
August 31, 1994 102
Philips Semiconductors Linear Products Product specification
Dual operational transconductance amplifier NE5517/5517A
15k
V
C
+V
CC
+V
CC INT
+V
CC
+ +
V
IN
NE5517/A NE5517/A
100k
200pF
C 2C
100pF
V
R
OUT
A
200
R
100k
A
R
-V
200 R
CC
A 10k 10k
100k 200
200
-V
CC
-V INT
CC
NOTE:
RA gM
fO +
(R ) RA) 2p C
Figure 10. Butterworth Filter 2nd Order
1
15k
16
V
C
+V
CC
+V
CC INT
10k 14 +V
3 CC
+ +
11
5
7
12 10
2
NE5517/A 15 NE5517/A
LOW
20k
PASS
6
V
800pF OUT
800pF
13
9
1k
-V
1k CC
5.1k
20k
20k
5.1k
-V
CC
-V
CC
INT
BANDPASS OUT
Figure 11. State Variable Filter
30k
+V
CC
V
C
+V
INT
CC +V
CC INT
47k
13 +V
4 CC
11
1 5
7
12 10
NE5517/A NE5517/A
16
3 + C +
6
8
0.1F
14
V
9 OUT2
-V
CC
20k
10k
-V
CC
-V V INT
CC OUT1
GAIN
CONTROL
Figure 12. Triangle-Square Wave Generator (VCO)
August 31, 1994 103
Philips Semiconductors Linear Products Product specification
Dual operational transconductance amplifier NE5517/5517A
I I
C B
470k
1
+V
CC
V
C
16
+V
INT
CC +V INT +V
CC
CC
47k
13
30k
4
+
11
5
7
12 10
2 NE5517/A NE5517/A
3
C
6
+
8
0.1F
14
R R
1 -V 2
CC
20k
30k
30k
-V
CC
-V V
CC OUT1
V
NOTE: OUT2
INT
(VC * 0.8) R1 2VPK x C 2VPKxC IC
VPK + IC t t IB
R1 ) R2 TH + IB TL + IC fOSC 2VPKxC
Figure 13. Sawtooth Pulse VCO
August 31, 1994 104
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