DATASHEET

CA3280, CA3280A
®
Data Sheet
May 2002
Dual, 9MHz, Operational
Transconductance Amplifier (OTA)
FN1174.6
Features
• Low Initial Input Offset Voltage: 500µV (Max) (CA3280A)
The CA3280 and CA3280A types consist of two variable
operational amplifiers that are designed to substantially reduce
the initial input offset voltage and the offset voltage variation
with respect to changes in programming current. This design
results in reduced “AGC thump,” an objectionable characteristic
of many AGC systems. Interdigitation, or crosscoupling, of
critical portions of the circuit reduces the amplifier dependence
upon thermal and processing variables.
The CA3280 has all the generic characteristics of an
operational voltage amplifier except that the forward transfer
characteristics is best described by transconductance rather
than voltage gain, and the output is current, not voltage. The
magnitude of the output current is equal to the product of
transconductance and the input voltage. This type of
operational transconductance amplifier was first introduced in
1969, and it has since gained wide acceptance as a gateable,
gain controlled building block for instrumentation and audio
applications, such as linearization of transducer outputs,
standardization of widely changing signals for data processing,
multiplexing, instrumentation amplifiers operating from the
nanopower range to high current and high speed comparators.
For additional application information on this device and on
OTAs in general, please refer to Application Notes: AN6818,
AN6668, and AN6077.
• Low Offset Voltage Change vs IABC: <500µV (Typ)
for All Types
• Low Offset Voltage Drift: 5µV/oC (Max) (CA3280A)
• Excellent Matching of the Two Amplifiers for All
Characteristics
• Internal Current-Driven Linearizing Diodes Reduce the
External Input Current to an Offset Component
• Flexible Supply Voltage Range . . . . . . . . . . ±2V to ±15V
Applications
• Voltage Controlled Amplifiers
• Voltage Controlled Oscillators
• Multipliers
• Demodulators
• Sample and Hold
• Instrumentation Amplifiers
• Function Generators
• Triangle Wave-to-Sine Wave Converters
• Comparators
• Audio Preamplifier
Pinout
CA3280 (PDIP)
TOP VIEW
ID, A1 1
A1
+
-
EMITTER, A1 2
Functional Diagram
16 +IN, A1
15 -IN, A1
V- 4
13 OUT, A1
NC 5
12 OUT, A2
-
11 V+, A2
IABC, A2 6
EMITTER, A2 7
14
1/2 CA3280
11
14 V+, A1
IABC, A1 3
-
10 -IN, A2
+
9 +IN, A2
A2
ID, A2 8
15
10
7
2
+ 16
13
9
2K
2K
12
1
Ordering Information
8
4
PART NUMBER
CA3280AE
CA3280E
TEMP.
RANGE (oC)
PACKAGE
PKG.
NO.
-55 to 125
16 Ld PDIP
E16.3
0 to 70
16 Ld PDIP
E16.3
1
3
6
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2002. All Rights Reserved
CA3280, CA3280A
.
Absolute Maximum Ratings
Thermal Information
Supply Voltage (Between V+ and V-) . . . . . . . . . . . . . . . . . . . .+36V
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V
Input Voltage Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V+ to VInput Current at ID = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100µA
Amplifier Bias Current (IABC) . . . . . . . . . . . . . . . . . . . . . . . . . . 10mA
Output Short Circuit Duration (Note 2). . . . . . . . . . . . . . . . Indefinite
Linearizing Diode Bias Current, ID . . . . . . . . . . . . . . . . . . . . . . . 5mA
Peak Input Current with Linearizing Diode. . . . . . . . . . . . . . . . . . ±ID
Thermal Resistance (Typical, Note 1)
θJA (oC/W)
θJC (oC/W)
PDIP Package . . . . . . . . . . . . . . . . . . .
90
N/A
Maximum Junction Temperature (Plastic Package) . . . . . . . .150oC
Maximum Storage Temperature Range . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300oC
Operating Conditions
Temperature Range
CA3280 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0oC to 70oC
CA3280A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55oC to 125oC
Supply Voltage Range (Typ) . . . . . . . . . . . . . . . . . . . . . ±2V to ±15V
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE:
1. θJA is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
2. Short circuit may be applied to ground or to either supply.
For Equipment Design, at TA = 25oC, VSUPPLY = ±15V, Unless Otherwise Specified
Electrical Specifications
CA3280
PARAMETER
SYMBOL
Input Offset Voltage
VIO
|∆VIO|
Input Offset Voltage Drift
TEST CONDITIONS
CA3280A
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
IABC = 1mA
-
-
3
-
-
0.5
mV
IABC = 100µA
-
0.7
3
-
0.25
0.5
mV
IABC = 10µA
-
-
3
-
-
0.5
mV
IABC = 1mA to 10µA,
TA = Full Temp. Range
-
0.8
4
-
0.8
1.5
mV
IABC = 1µA to 1mA
-
0.5
1
-
0.5
1
mV
IABC = 100µA, TA = Full
Temperature Range
-
5
-
-
3
5
µV/oC
Amplifier Bias Voltage
VABC
IABC = 100µA
-
1.2
-
-
1.2
-
V
Peak Output Voltage
VOM+
IABC = 500µA
12
13.7
-
12.5
13.7
-
V
12
-14.3
-
-13.3
-14.3
-
V
12
13.9
-
12.5
13.9
-
V
12
-14.5
-
-13.5
-14.5
-
V
-13
-
13
-13
-
13
V
10Hz
-
20
-
-
20
-
nV/√Hz
1kHz
-
8
-
-
8
-
nV/√Hz
10kHz
-
7
-
-
7
-
nV/√Hz
VOMVOM+
IABC = 5µA
VOMCommon Mode Input Voltage
Range
Noise Voltage
VICR
IABC = 100µA
eN
IABC = 500µA
Input Offset Current
IIO
IABC = 500µA
-Z
0.3
0.7
-
0.3
0.7
µA
Input Bias Current
IIB
IABC = 500µA
-
1.8
5
-
1.8
5
µA
IABC = 500µA, TA = Full
Temperature Range
-
3
8
-
3
8
µA
2
CA3280, CA3280A
For Equipment Design, at TA = 25oC, VSUPPLY = ±15V, Unless Otherwise Specified (Continued)
Electrical Specifications
CA3280
PARAMETER
SYMBOL
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
Source
350
410
650
350
410
650
µA
Sink
-350
-410
-650
-350
-410
-650
µA
Source
3
4.1
7
3
4.1
7
µA
IOM-
Sink
-3
-4.1
-7
-3
-4.1
-7
µA
IOM -,
IOM+
IABC = 500µA, TA = Full
Temperature Range
350
450
550
350
450
550
µA
ID = 100µA
-
10
-
-
10
-
µA
Offset Current
ID = 10µA
-
0.5
1
-
0.5
1
µA
Dynamic Impedance
ID = 100µA
-
700
-
-
700
-
Ω
IABC = 100µA
250
400
800
250
400
800
µA
IABC = 500µA
-
2
2.4
-
2
2.4
mA
IABC = 0, VO = 0V
-
0.015
0.1
-
0.015
0.1
nA
IABC = 0, VO = 30V
-
0.15
1
-
0.15
1
nA
Peak Output Current
IOM+
TEST CONDITIONS
CA3280A
IABC = 500µA
IOMIOM+
Peak Output Current Sink and
Source
Linearization Diodes
Diode Network Supply Current
Amplifier Supply Current
(Per Amplifier)
I+
Amplifier Output Leakage Current
IOL
IABC = 5µA
Common Mode Rejection Ratio
CMRR
IABC = 100µA
80
100
-
94
100
-
dB
Power Supply Rejection Ratio
PSRR
IABC = 100µA
86
105
-
94
105
-
dB
IABC = 100µA,
RL = ∞, VO = 20VP-P
94
100
-
94
100
-
dB
50
100
-
50
100
-
kV/V
Open Loop Voltage Gain
AOL
Forward Transconductance
GM
IABC = 50µA, Large Signal
-
0.8
1.2
-
0.8
1.2
mS
gM
IABC = 1mA, Small Signal
-
16
22
-
16
22
mS
RI
IABC = 10µA
0.5
-
-
0.5
-
-
MΩ
f = 1kHz
-
94
-
-
94
-
dB
THD
f = 1kHz, IABC = 1.5mA,
RL = 15kΩ, VO = 20VP-P
-
0.4
-
-
0.4
-
%
Bandwidth
fT
IABC = 1mA, RL = 100Ω
-
9
-
-
9
-
MHz
Slew Rate, Open Loop
SR
IABC = 1mA
-
125
-
-
125
-
V/µs
Capacitance
CI
IABC = 100µA
Input
-
4.5
-
-
4.5
-
pF
Output
-
7.5
-
-
7.5
-
pF
-
63
-
-
63
-
MΩ
Input Resistance
Channel Separation
Open Loop Total
Harmonic Distortion
CO
Output Resistance
RO
3
IABC = 100µA
CA3280, CA3280A
Test Circuits and Waveforms
V+
+30V
INPUT
16
14
30V
0V
15
I
TEST
POINT
1/2
CA3280
+
16
15
13
+
1/2
CA3280
-
1kΩ
1
0.1
µF
OUTPUT
13
3
4
4
0.1µF
14
30kΩ
V-
V+
10kΩ
3
30kΩ
1kΩ
FIGURE 1. LEAKAGE CURRENT TEST CIRCUIT
FIGURE 2. CHANNEL SEPARATION TEST CIRCUIT
V+
15V
14
10kΩ
16
IOUT
1/2
CA3280
13
10kΩ
15
4
3
1kΩ
1
V-15V
VIN
IABC
IABC = 650µA, ID = 200µA; Vertical = 200µA/Div.;
Horizontal = 1V/Div.
IDIODE
FIGURE 3A. EFFECTS OF DIODE LINEARIZATION, WITH DIODE PROGRAMMING TERMINAL ACTIVE
V+
15V
11
10kΩ
9
1/2
CA3280
12
IOUT
10kΩ
10
6
4
1kΩ
8
IDIODE
IABC
V-15V
VIN
IABC = 650µA; ID = 0; Vertical = 200µA/Div.;
Horizontal = 25mV/Div.
FIGURE 3B. WITH DIODE PROGRAMMING TERMINAL CUTOFF
FIGURE 3. CA3280 TRANSFER CHARACTERISTICS
4
CA3280, CA3280A
Application Information
Figures 4 and 5 show the equivalent circuits for the current
source and linearization diodes in the CA3280. The current
through the linearization network is approximately equal to the
programming current. There are several advantages to driving
these diodes with a current source. First, only the offset current
from the biasing network flows through the input resistor.
Second, another input is provided to extend the gain control
dynamic range. And third, the input is truly differential and can
accept signals within the common mode range of the CA3280.
Typical Applications
The structure of the variable operational amplifier eliminates
the need for matched resistor networks in differential to single
ended converters, as shown in Figure 6. A matched resistor
network requires ratio matching of 0.01% or trimming for 80dB
of common-mode rejection. The CA3280, with its excellent
common mode rejection ratio, is capable of converting a small
(±25mV) differential input signal to a single-ended output
without the need for a matched resistor network.
Figure 7 shows the CA3280 in a typical gain control application.
Gain control can be performed with the amplifier bias current
(lABC). With no diode bias current, the gain is merely gMRL. For
example, with an lABC of 1mA, the gM is approximately 16mS.
With the CA3280 operating into a 5kΩ resistor, the gain is 80.
The need for external buffers can be eliminated by the use of
low value load resistors, but the resulting increase in the
required amplifier bias current reduces the input impedance
of the CA3280. The linearization diode impedance also
decreases as the diode bias current increases, which further
loads the input. The diodes, in addition to acting as a
linearization network, also operate as an additional
attenuation system to accommodate input signals in the volt
range when they are applied through appropriate input
resistors.
Figure 10 shows a triangle wave to sine wave converter
using the CA3280. Two 100kΩ resistors are connected
between the differential amplifier emitters and V+ to reduce
the current flow through the differential amplifier. This allows
the amplifier to fully cut off during peak input signal
excursions. THD is appropriately 0.37% for this circuit.
RD = SMALL SIGNAL DIODE
IMPEDANCE
V+
RD ≈
70
52Ω
ID(mA) x 1.34 = ID
RD
VOA
VOA
ID
IABC
ID
IABC
V-
FIGURE 4. VOA SHOWING LINEARIZATION DIODES AND
CURRENT DRIVE
FIGURE 5. BLOCK DIAGRAM OF LINEARIZED VOA
10VP-P
INPUT
+15V
V+ = +15V
OUTPUT
21VP-P
14mV AGC
FEEDTHRU
400µV
NOISE AT
MAX GAIN
68kΩ
600Ω
68kΩ
1
16
3
2kΩ
16
DIFFERENTIAL
INPUT 2kΩ
15
14
10kΩ
14
+
1/2
CA3280
V+
13
-
SINGLEENDED
OUTPUT
330kΩ
+
1/2
CA3280
-
15
100kΩ
13
4
15kΩ
4
10kΩ
1
V-
3
10kΩ
20kΩ
V- = -15V
-15V
FIGURE 6. DIFFERENTIAL TO SINGLE ENDED CONVERTER
5
VOLTAGE
CONTROL
FIGURE 7. TYPICAL GAIN CONTROL CIRCUIT
CA3280, CA3280A
3
+15V
2kΩ
16
+
1/2
CA3280
33pF
51Ω
10kΩ
14
13
-
15
1800pF
2kΩ
2kΩ
6
9
51Ω
10kΩ
+
1/2
CA3280
33pF
-
10
-15V
1N914
14
4
6
7
OUTPUT
100kΩ
12
300pF
10kΩ
5
100Ω
1
1
3
2
TO 10kΩ
6
1/2 CD4013
4
8
TO 10kΩ
3
-15V
0.05µF
FIGURE 8. TWO CHANNEL LINEAR MULTIPLEXER
V+
3.6kΩ
V+ = +7.5V
14
16
0.1µF
+
1/2
CA3280
200Ω
15
13
3
V+
560kΩ
+
11
10
6
4
V+
-
6
1/2
CA3280
-
2
2.7kΩ
3.3kΩ
CA3160
15 - 115pF
3
910kΩ
V-
7
-
200Ω
100kΩ
V+
9
V-
+
8
4
0.1µF
100kΩ
12
1
VV- = -7.5V
V+
3.3kΩ
V10kΩ
MAX FREQ.
SET
5.6kΩ
4 - 60pF
500Ω
1kΩ
MIN FREQ. SET
2kΩ
1N914
1N914
FIGURE 9. CA3280 USED IN CONJUNCTION WITH A CA3160 TO PROVIDE A FUNCTION GENERATOR WITH A TUNABLE RANGE OF
2Hz TO 1MHz
+15V
170mVP-P
2kΩ
16
15
0.1
µF
30kΩ
14
6.8
1
MΩ MΩ
3
+
1/2
CA3280
13
100kΩ
-
2
+15V
+15V
51Ω
11
-15V
+15V
1MΩ
10
100kΩ
-15V
200Ω
6
9
2kΩ
+
1/2
CA3280
7
12
3.9
kΩ
100kΩ
4
-15V
FIGURE 10. TRIANGLE WAVE-TO-SINE WAVE CONVERTER
6
CA3280, CA3280A
Typical Performance Curves
IABC = 3mA
104
101
TA = 25oC
SUPPLY CURRENT (mA)
SMALL SIGNAL FORWARD
TRANSCONDUCTANCE (mS)
105
IABC = 300µA
103
IABC = 30µA
102
IABC = 3.0µA
101
IABC = 0.3µA
1
I
= 0.03µA
0.1 ABC
101 102
103
104
105
106
107
108
TA = 25oC
VS = ±15V
1
10-1
10-2
10-1
109
101
1
FIGURE 11. AMPLIFIER GAIN vs FREQUENCY
2
INPUT OFFSET VOLTAGE (mV)
INPUT OFFSET CURRENT (nA)
FIGURE 12. SUPPLY CURRENT vs DIODE CURRENT
VS = ±15V
TA = -55oC
TA = 25oC
TA = 125oC
102
101
1
101
1
102
1
0
TA = 125oC
TA = 25oC
TA = -55oC
-1
-2
TA = 125oC
-3
-4
-5
103
101
102
AMPLIFIER BIAS CURRENT (µA)
1
AMPLIFIER BIAS CURRENT (µA)
FIGURE 13. INPUT OFFSET CURRENT vs AMPLIFIER BIAS
CURRENT
103
FIGURE 14. INPUT OFFSET VOLTAGE vs AMPLIFIER BIAS
CURRENT
16
106
VS = ±15V
105
INPUT CURRENT (pA)
15
PEAK OUTPUT VOLTAGE (V)
103
DIODE CURRENT (µA)
FREQUENCY (Hz)
103
102
14
13
TA = 125oC
TA = 25oC
TA = -55oC
0
-13
TA = 125oC
TA = 25oC
TA = -55oC
-14
TA = 125oC
104
103
102
TA = 25oC
101
-15
-16
1
101
102
103
AMPLIFIER BIAS CURRENT (µA)
FIGURE 15. PEAK OUTPUT VOLTAGE vs AMPLIFIER BIAS
CURRENT
7
1
0
1
2
3
4
5
6
7
8
9
DIFFERENTIAL INPUT VOLTAGE (V)
FIGURE 16. INPUT CURRENT vs INPUT DIFFERENTIAL
VOLTAGE
10
CA3280, CA3280A
Typical Performance Curves
(Continued)
1800
AMPLIFIER BIAS VOLTAGE (mV)
LEAKAGE CURRENT (nA)
104
103
V9 = V10 = V12 = 30V
102
10
1
V9 = V10 = V12 = 0V
10-1
10-2
-75
VS = ±15V
1600
TA = -55oC
1400
TA = 25oC
1200
1000
TA = 100oC
800
TA = 125oC
600
400
-50
-25
0
25
50
75
100
125
150 175
101
1
TEMPERATURE (oC)
FIGURE 18. AMPLIFIER BIAS VOLTAGE vs AMPLIFIER BIAS
CURRENT
103
TA = 25oC
20
PEAK OUTPUT CURRENT (µA)
1/ f NOISE VOLTAGE (nV/√Hz)
22
18
16
14
12
10
IABC = 500µA
8
6
4
VS = ±15V
TA = -55oC
TA = 25oC
TA = 125oC
102
101
TA = 125oC
TA = -55oC
TA = 25oC
2
1
0
101
102
103
104
105
101
1
FIGURE 19. 1/f NOISE vs FREQUENCY
103
FIGURE 20. PEAK OUTPUT CURRENT vs AMPLIFIER BIAS
CURRENT
105
106
TA = 25oC
VS = +15V
105
SMALL SIGNAL FORWARD
TRANSCONDUCTANCE (µS)
DIODE RESISTANCE (Ω)
102
AMPLIFIER BIAS CURRENT (µA)
FREQUENCY (Hz)
104
103
102
101
10-1
103
AMPLIFIER BIAS CURRENT (µA)
FIGURE 17. LEAKAGE CURRENT vs TEMPERATURE
24
102
1
101
102
103
DIODE CURRENT (µA)
FIGURE 21. DIODE RESISTANCE vs DIODE CURRENT
8
104
104
TA = -55oC
TA = 25oC
TA = 125oC
103
102
101
1
10-1
10-3
10-2
10-1
1
101
102
103
104
AMPLIFIER BIAS CURRENT (µA)
FIGURE 22. AMPLIFIER GAIN vs AMPLIFIER BIAS CURRENT
CA3280, CA3280A
Typical Performance Curves
104
VS = ±15V
VS = ±15V
103
INPUT BIAS CURRENT (nA)
SUPPLY CURRENT (µA)
104
(Continued)
102
TA = 125oC
101
TA = -55oC, 25oC
1
103
102
TA = 125oC
TA = 25oC
101
TA = -55oC
10-1
10-1
101
1
102
103
AMPLIFIER BIAS CURRENT (µA)
FIGURE 23. SUPPLY CURRENT vs AMPLIFIER BIAS CURRENT
9
1
10-1
1
101
102
AMPLIFIER BIAS CURRENT (µA)
FIGURE 24. INPUT BIAS CURRENT vs AMPLIFIER BIAS
CURRENT
103
CA3280, CA3280A
Dual-In-Line Plastic Packages (PDIP)
N
E16.3 (JEDEC MS-001-BB ISSUE D)
E1
INDEX
AREA
1 2 3
16 LEAD DUAL-IN-LINE PLASTIC PACKAGE
N/2
INCHES
-B-
SYMBOL
-AE
D
BASE
PLANE
-C-
A2
SEATING
PLANE
A
L
D1
e
B1
D1
eA
A1
eC
B
0.010 (0.25) M
C
L
C A B S
C
eB
NOTES:
1. Controlling Dimensions: INCH. In case of conflict between English and
Metric dimensions, the inch dimensions control.
MILLIMETERS
MIN
MAX
MIN
MAX
NOTES
A
-
0.210
-
5.33
4
A1
0.015
-
0.39
-
4
A2
0.115
0.195
2.93
4.95
-
B
0.014
0.022
0.356
0.558
-
B1
0.045
0.070
1.15
1.77
8, 10
C
0.008
0.014
0.204
0.355
-
D
0.735
0.775
18.66
19.68
5
D1
0.005
-
0.13
-
5
E
0.300
0.325
7.62
8.25
6
E1
0.240
0.280
6.10
7.11
5
e
0.100 BSC
2.54 BSC
-
3. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication No. 95.
eA
0.300 BSC
7.62 BSC
6
eB
-
0.430
-
10.92
7
4. Dimensions A, A1 and L are measured with the package seated in JEDEC seating plane gauge GS-3.
L
0.115
0.150
2.93
3.81
4
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
5. D, D1, and E1 dimensions do not include mold flash or protrusions.
Mold flash or protrusions shall not exceed 0.010 inch (0.25mm).
6. E and eA are measured with the leads constrained to be perpendicular to datum -C- .
N
16
16
9
Rev. 0 12/93
7. eB and eC are measured at the lead tips with the leads unconstrained.
eC must be zero or greater.
8. B1 maximum dimensions do not include dambar protrusions. Dambar
protrusions shall not exceed 0.010 inch (0.25mm).
9. N is the maximum number of terminal positions.
10. Corner leads (1, N, N/2 and N/2 + 1) for E8.3, E16.3, E18.3, E28.3,
E42.6 will have a B1 dimension of 0.030 - 0.045 inch (0.76 - 1.14mm).
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
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10
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