INTERSIL CA3280AF3

CA3280, CA3280A
Data Sheet
September 1998
File Number
1174.4
Dual, 9MHz, Operational
Transconductance Amplifier (OTA)
Features
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.
• Low Offset Voltage Change vs IABC: <500µV (Typ)
for All Types
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.
• Flexible Supply Voltage Range. . . . . . . . . . . ±2V to ±15V
For additional application information on this device and on
OTAs in general, please refer to Application Notes: AN6818,
AN6668, and AN6077.
• Low Initial Input Offset Voltage: 500µV (Max) (CA3280A)
• 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
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
Ordering Information
CA3280
(PDIP, CERDIP)
TOP VIEW
ID, A1 1
A1
+
-
EMITTER, A1 2
IABC, A1 3
PART NUMBER
16 +IN, A1
15 -IN, A1
CA3280E
14 V+, A1
CA3280AF3
V- 4
13 OUT, A1
NC 5
12 OUT, A2
PACKAGE
PKG.
NO.
-55 to 125
16 Ld PDIP
E16.3
0 to 70
16 Ld PDIP
E16.3
16 Ld CERDIP
F16.3
-55 to 125
11 V+, A2
IABC, A2 6
EMITTER, A2 7
CA3280AE
TEMP.
RANGE (oC)
A2
ID, A2 8
1
-
10 -IN, A2
+
9 +IN, A2
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Copyright © Intersil Corporation 1999
CA3280, CA3280A
.
Functional Diagram
14
1/2 CA3280
11
-
15
10
7
2
+ 16
13
9
2K
2K
12
1
8
4
3
2
6
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 1). . . . . . . . . . . . . . . . Indefinite
Linearizing Diode Bias Current, ID . . . . . . . . . . . . . . . . . . . . . . . 5mA
Peak Input Current with Linearizing Diode. . . . . . . . . . . . . . . . . . ±ID
Thermal Resistance (Typical, Note 2)
θJA (oC/W) θJC (oC/W)
CERDIP Package. . . . . . . . . . . . . . . . .
65
16
PDIP Package . . . . . . . . . . . . . . . . . . .
100
N/A
Maximum Junction Temperature (CERDIP Package). . . . . . . . .175oC
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.
NOTES:
1. Short circuit may be applied to ground or to either supply.
2. θJA is measured with the component mounted on an evaluation PC board in free air.
For Equipment Design, at TA = 25oC, VSUPPLY = ±15V, Unless Otherwise Specified
Electrical Specifications
CA3280
PARAMETER
SYMBOL
Input Offset Voltage
VIO
Input Offset Voltage Drift
|∆VIO|
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 = 500mA
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
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
Sink
-3
-4.1
-7
-3
-4.1
-7
µA
Peak Output Current
IOM+
IABC = 500µA
IOMIOM+
IOM-
3
IABC = 5µA
CA3280, CA3280A
For Equipment Design, at TA = 25oC, VSUPPLY = ±15V, Unless Otherwise Specified (Continued)
Electrical Specifications
CA3280
PARAMETER
SYMBOL
CA3280A
TEST CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
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 Sink and
Source
IOM -,
IOM+
Linearization Diodes
Diode Network Supply Current
Amplifier Supply Current
(Per Amplifier)
I+
Amplifier Output Leakage Current
IOL
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
IABC = 100µA
Test Circuits and Waveforms
V+
+30V
INPUT
16
14
30V
0V
I
TEST
POINT
15
16
1/2
CA3280
+
15
13
+
1/2
CA3280
-
4
1
1kΩ
OUTPUT
13
3
4
0.1
µF
0.1µF
14
30kΩ
V-
V+
10kΩ
3
30kΩ
1kΩ
FIGURE 1. LEAKAGE CURRENT TEST CIRCUIT
4
FIGURE 2. CHANNEL SEPARATION TEST CIRCUIT
CA3280, CA3280A
Test Circuits and Waveforms
(Continued)
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
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
5
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
CA3280, CA3280A
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
6
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
14
4
6
7
OUTPUT
100kΩ
12
-
10
-15V
1N914
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
200Ω
13
3
15
910kΩ
560kΩ
+
2
2.7kΩ
3.3kΩ
CA3160
15 - 115pF
3
VV+
7
-
200Ω
V+
0.1µF
+
1/2
CA3280
100kΩ
V+
11
10
6
-
6
1/2
CA3280
4
9
V-
+
8
4
0.1µF
100kΩ
12
1
VV- = -7.5V
V+
3.3kΩ
V10kΩ
MAX FREQ.
SET
5.6kΩ
500Ω
4 - 60pF
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
1
6.8
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
7
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
TA = 25oC
VS = ±15V
1
10-1
IABC = 0.3µA
1
I
= 0.03µA
0.1 ABC
101 102
103
104
105
106
107
108
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
15
105
INPUT CURRENT (pA)
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
AMPLIFIER BIAS CURRENT (µA)
FIGURE 15. PEAK OUTPUT VOLTAGE vs AMPLIFIER BIAS
CURRENT
8
103
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 (µmS)
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
9
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
1
10-1
1
102
AMPLIFIER BIAS CURRENT (µA)
FIGURE 24. INPUT BIAS CURRENT vs AMPLIFIER BIAS
CURRENT
Metallization Mask Layout
Dimensions in parentheses are in millimeters and derived from
the basic inch dimensions as indicated. Grid graduations are in
mils (10-3 inch).
The photographs and dimensions represent a chip when it is
part of the wafer. When the wafer is cut into chips, the cleavage
angles are 57o instead of 90o with respect to the face of the
chip. Therefore, the isolated chip is actually 7 mils (0.17mm)
larger in both dimensions.
10
101
103