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Part: CA3280E
Category:
Analog & Mixed-Signal Processing
-> Amplifiers
-> Operational Amplifiers
Description: Dual, 9MHz, Operational Transconductance Amplifier (OTA)
Company: Intersil Corporation
Datasheet: Download CA3280E datasheet File size : 1382 kB
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®
CA3280, CA3280A
D a ta Sheet Ma y 2002 FN1174.6
Dual, 9MHz, Operational Transconductance Amplifier (OTA)
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.
Features
· Low Initial Input Offset Voltage: 500µV (Max) (CA3280A) · 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 EMITTER, A1 2 IABC, A1 3 V- 4 NC 5 IABC, A2 6 EMITTER, A2 7 ID, A2 8 A2 A1 + 16 +IN, A1 15 -IN, A1 14 V+, A1 13 OUT, A1 12 OUT, A2 11 V+, A2
Functional Diagram
-
1/2 CA3280
14
11
-
15
10
+ 16
+
10 -IN, A2 9 +IN, A2 9
1
7 2
13 2K 2K
12
Ordering Information
PART NUMBER CA3280AE CA328 0E TEMP. RANGE (oC) -55 to 125 0 to 70 PACKAGE 16 Ld PDIP 16 Ld PDIP PKG. NO. E16.3 E16.3
8
4 3
6
1
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
Thermal Resistance (Typical, Note 1) JA (oC/W) JC (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
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
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. JA 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.
Electrical Specifications
For Equipment Design, at TA = 25oC, VSUPPLY = ±15V, Unless Otherwise Specified CA3280 CA3280A MAX 3 3 3 4 1 13 0.7 5 8 MIN 1 2. 5 - 13.3 1 2. 5 - 13.5 -13 TYP 0. 2 5 0.8 0. 5 3 1. 2 13.7 -14.3 13.9 -14.5 20 8 7 0.3 1. 8 3 MAX 0.5 0. 5 0. 5 1. 5 1 5 13 0. 7 5 8 UNITS mV mV mV mV mV µ V /o C V V V V V V nV/Hz nV/Hz nV/Hz µA µA µA
PARAMETER Input Offset Voltage
SYMBOL VI O
TEST CONDITIONS IABC = 1mA IABC = 100µA IABC = 10µA IABC = 1mA to 10µA, TA = Full Temp. Range
MIN 12 12
TYP 0.7 0. 8 0.5 5 1. 2 13.7 -14.3 13.9 -14.5 20 8 7 0. 3 1. 8 3
Input Offset Voltage Drift
|VIO|
IABC = 1µA to 1mA IABC = 100µA, TA = Full Temperature Range
Amplifier Bias Voltage Peak Output Voltage
VABC VOM+ VOMVOM+ VOM-
IABC = 100µA IABC = 500µA
IABC = 5µA
12 12
Common Mode Input Voltage Range Noise Voltage
VICR eN
IABC = 100µA IABC = 500µA 10Hz 1kHz 10kHz
-13 -Z -
Input Offset Current Input Bias Current
IIO IIB
IABC = 500µA IABC = 500µA IABC = 500µA, TA = Full Temperature Range
2
CA3280, CA3280A
Electrical Specifications
For Equipment Design, at TA = 25oC, VSUPPLY = ±15V, Unless Otherwise Specified (Continued) CA3280 PARAMETER Peak Output Current SYMBOL IOM+ IOMIOM+ IOMPeak Output Current Sink and Source Linearization Diodes Offset Current Dynamic Impedance Diode Network Supply Current Amplifier Supply Current (Per Amplifier) Amplifier Output Leakage Current I+ IOL IOM - , IOM+ IABC = 5µA TEST CONDITIONS IABC = 500µA Source Sink Source Sink IABC = 500µA, TA = Full Temperature Range ID = 100µA ID = 10µA ID = 100µA IABC = 100µA IABC = 500µA IABC = 0, VO = 0V IABC = 0, VO = 30V Common Mode Rejection Ratio Power Supply Rejection Ratio Open Loop Voltage Gain C MRR PSRR AOL IABC = 100µA IABC = 100µA IABC = 100µA, RL = , VO = 20VP-P IABC = 50µA, Large Signal IABC = 1mA, Small Signal IABC = 10µA f = 1kHz THD fT SR CI CO Output Resistance RO IABC = 100µA f = 1kHz, IABC = 1.5mA, RL = 15k, VO = 20VP-P IABC = 1mA, RL = 100 IABC = 1mA IABC = 100µA I nput Output MIN 350 -350 3 -3 350 250 80 86 94 50 0. 5 TYP 410 -410 4.1 -4.1 450 10 0. 5 700 400 2 0. 0 1 5 0. 1 5 100 105 100 100 0. 8 16 94 0. 4 9 125 4. 5 7. 5 63 MAX 650 -650 7 -7 550 1 800 2. 4 0.1 1 1.2 22 MIN 350 -350 3 -3 350 250 94 94 94 50 0. 5 CA3280A TYP 410 -410 4.1 -4.1 450 10 0. 5 700 400 2 0.015 0. 1 5 100 105 100 100 0.8 16 94 0. 4 9 125 4.5 7.5 63 MAX 650 -650 7 -7 550 1 800 2. 4 0.1 1 1. 2 22 UNITS µA µA µA µA µA µA µA µA mA nA nA dB dB dB k V/V mS mS M dB % MHz V /µ s pF pF M
Forward Transconductance
GM gM
Input Resistance Channel Separation Open Loop Total Harmonic Distortion Bandwidth Slew Rate, Open Loop Capacitance
RI
3
CA3280, CA3280A Test Circuits and Waveforms
V+ +30V INPUT 16 30V 0V 14 I TEST POINT 15 1/2 CA3280 + 4 1 3 1k 30k 14 + 1/2 CA3280 0.1µF O U TP U T 13 3 30k VV+ 10k
-
13 0.1 µF
15
-
16
4 1k
FIGURE 1. LEAKAGE CURRENT TEST CIRCUIT
FIGURE 2. CHANNEL SEPARATION TEST CIRCUIT
V+ 15V 14 10k 16 1/2 CA3280 15 4 3 1 IABC IDIODE V-15V 1k VI N 13 IOUT
10k
IABC = 650µA, ID = 200µA; Vertical = 200µA/Div.; Horizontal = 1V/Div.
FIGURE 3A. EFFECTS OF DIODE LINEARIZATION, WITH DIODE PROGRAMMING TERMINAL ACTIVE
V+ 15V 11 10k 9 1/2 CA3280 10 6 4 8 IDIODE IABC V-15V VIN 1k 12 IOUT
10k
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. (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 5k 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 100k 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.
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
V+ RD = SMALL SIGNAL DIODE IMPEDANCE RD 70 52 ID(mA) x 1.34 = ID
RD VOA VOA
IABC ID V-
ID
I ABC
FIGURE 4. VOA SHOWING LINEARIZATION DIODES AND CURRENT DRIVE
+15V
FIGURE 5. BLOCK DIAGRAM OF LINEARIZED VOA
10VP-P INPUT 68k 600 10k 16 V+ SINGLEENDED O U TP U T 10k 330k 100k V15
V+ = +15V O U TP U T 21VP-P 14mV AGC FEEDTHRU 400µV NOISE AT MAX GAIN 13 4 15k
68k 14 2k 16 DIFFERENTIAL INPUT 2k 15 3
1
14
+ 1/2 CA3280
+ 1/2 CA3280
13
3
4 1
10k 20k V- = -15V
-15V
VOLTAGE CONT ROL
FIGURE 6. DIFFERENTIAL TO SINGLE ENDED CONVERTER
FIGURE 7. TYPICAL GAIN CONTROL CIRCUIT
5
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