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1
TM
File Number
1320.6
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright
Intersil Corporation 2000
CA3420, CA3420A
0.5MHz, Low Supply Voltage, Low Input
Current BiMOS Operational Amplifiers
The CA3420A and CA3420 are integrated circuit operational
amplifiers that combine PMOS transistors and bipolar
transistors on a single monolithic chip. The CA3420A and
CA3420 BiMOS operational amplifiers feature gate
protected PMOS transistors in the input circuit to provide
very high input impedance, very low input currents (less than
1pA). The internal bootstrapping network features a unique
guardbanding technique for reducing the doubling of leakage
current for every 10
o
C increase in temperature. The CA3420
series operates at total supply voltages from 2V to 20V
either single or dual supply. These operational amplifiers are
internally phase compensated to achieve stable operation in
the unity gain follower configuration. Additionally, they have
access terminals for a supplementary external capacitor if
additional frequency roll-off is desired. Terminals are also
provided for use in applications requiring input offset voltage
nulling. The use of PMOS in the input stage results in
common mode input voltage capability down to 0.45V below
the negative supply terminal, an important attribute for single
supply application. The output stage uses a feedback OTA
type amplifier that can swing essentially from rail-to-rail. The
output driving current of 1.5mA (Min) is provided by using
nonlinear current mirrors.
Features
2V Supply at 300
A Supply Current
1pA Input Current (Typ) (Essentially Constant to 85
o
C)
Rail-to-Rail Output Swing (Drive
2mA into 1k
Load)
Pin Compatible with 741 Operational Amplifiers
Applications
pH Probe Amplifiers
Picoammeters
Electrometer (High Z) Instruments
Portable Equipment
Inaccessible Field Equipment
Battery-Dependent Equipment (Medical and Military)
Functional Diagram
Pinouts
CA3420 (PDIP)
TOP VIEW
CA3420 (METAL CAN)
TOP VIEW
Ordering Information
PART NUMBER
TEMP.
RANGE (
o
C)
PACKAGE
PKG.
NO.
CA3420AT
-55 to 125
8 Pin Metal Can
T8.C
CA3420E
-55 to 125
8 Ld PDIP
E8.3
MOS
BIPOLAR
X1
X1
MOS
BIPOLAR
OTA BUFFER
(X2)
HIGH GAIN
(50K)
BUFFER AMPS;
BOOTSTRAPPED
INPUT PROTECTION
NETWORK
-
+
1
2
3
4
8
7
6
5
+
V+
OFFSET NULL
INV.
INPUT
V-
NON-INV.
INPUT
STROBE
OUTPUT
OFFSET NULL
-
OUTPUT
OFFSET NULL
4
6
1
3
7
5
8
+
STROBE
V+
V-
NON-INV.
INPUT
INV.
INPUT
TAB
OFFSET NULL
2
-
Data Sheet
April 2000
2
Absolute Maximum Ratings
Thermal Information
Supply Voltage (V+ to V-). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22V
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15V
DC Input Voltage . . . . . . . . . . . . . . . . . . . . . . (V+ + 8V) to (V- -0.5V)
Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1mA
Output Short Circuit Duration (Note 1). . . . . . . . . . . . . . . . Indefinite
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . -55
o
C to 125
o
C
Thermal Resistance (Typical, Note 2)
JA
(
o
C/W)
JC
(
o
C/W)
PDIP Package . . . . . . . . . . . . . . . . . . .
105
N/A
Metal Can Package . . . . . . . . . . . . . . .
165
80
Maximum Junction Temperature (Metal Can Package). . . . . . . 175
o
C
Maximum Junction Temperature (Plastic Package) . . . . . . . 150
o
C
Maximum Storage Temperature Range . . . . . . . . . . -65
o
C to 150
o
C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300
o
C
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.
JA
is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
Typical Values Intended Only for Design Guidance, V
SUPPLY
=
10V, T
A
= 25
o
C
PARAMETER
SYMBOL
TEST CONDITIONS
CA3420A
CA3420
UNITS
Input Resistance
R
I
150
150
T
Input Capacitance
C
I
4.9
4.9
pF
Output Resistance
R
O
300
300
Equivalent Input Noise Voltage
e
N
f = 1kHz
R
S
= 100
62
62
nV/
Hz
f = 10kHz
38
38
nV/
Hz
Short-Circuit Current
Source
I
OM
+
2.6
2.6
mA
To Opposite Supply
Sink
I
OM
-
2.4
2.4
mA
Gain Bandwidth Product
f
T
0.5
0.5
MHz
Slew Rate
SR
0.5
0.5
V/
s
Transient Response
Rise Time
t
R
R
L
= 2k
, C
L
= 100pF
0.7
0.7
s
Overshoot
OS
15
15
%
Current from Terminal 8
To V-
I
8
+
20
20
A
To V+
I
8
-
2
2
mA
Electrical Specifications
For Equipment Design, At V
SUPPLY
=
1V, T
A
= 25
o
C, Unless Otherwise Specified
PARAMETER
SYMBOL
TEST
CONDITIONS
CA3420
CA3420A
UNITS
MIN
TYP
MAX
MIN
TYP
MAX
Input Offset Voltage
|V
IO
|
-
5
10
-
2
5
mV
Input Offset Current (Note 3)
|I
IO
|
-
0.01
4
-
0.01
4
pA
Input Current (Note 3)
|I
I
|
-
1
5
-
0.02
5
pA
Large Signal Voltage Gain
A
OL
R
L
= 10k
10
100
-
20
100
-
kV/V
80
100
-
86
100
-
dB
Common Mode Rejection Ratio
CMRR
-
560
1800
-
560
1000
V/V
55
65
-
60
65
-
dB
Common Mode Input Voltage Range
V
lCR
+
0.2
0.5
-
0.2
0.5
-
V
V
lCR
-
-
-1.3
-
-1
-1.3
-
V
Power Supply Rejection Ratio
PSRR
V
IO
/
V
-
100
1000
-
32
320
V/V
60
80
-
70
90
-
dB
Max Output Voltage
V
OM
+
R
L
=
0.90
0.95
-
0.90
0.95
-
V
V
OM
-
-0.85
-0.91
-
-0.85
-0.91
-
V
Supply Current
I+
-
350
650
-
350
650
A
Device Dissipation
P
D
-
0.7
1.1
-
0.7
1.1
mW
Input Offset Voltage Temperature Drift
V
lO
/
T
-
4
-
-
4
-
V/
o
C
NOTE:
3. The maximum limit represents the levels obtainable on high speed automatic test equipment. Typical values are obtained under laboratory conditions.
CA3420, CA3420A
3
Typical Applications
Picoammeter Circuit
The exceptionally low input current (typically 0.2pA) makes
the CA3420 highly suited for use in a picoammeter circuit.
With only a single 10G
resistor, this circuit covers the range
from
1.5pA. Higher current ranges are possible with suitable
switching techniques and current scaling resistors. Input
transient protection is provided by the 1M
resistor in series
with the input. Higher current ranges require that this resistor
be reduced. The 10M
resistor connected to pin 2 of the
CA3420 decouples the potentially high input capacitance
often associated with lower current circuits and reduces the
tendency for the circuit to oscillate under these conditions.
High Input Resistance Voltmeter
Advantage is taken of the high input impedance of the CA3420
in a high input resistance DC voltmeter. Only two 1.5V "AA"
type penlite batteries power this exceedingly high-input
resistance (>1,000,000M
) DC voltmeter. Full-scale deflection
is
500mV,
150mV, and
15mV. Higher voltage ranges are
easily added with external input voltage attenuator networks.
The meter is placed in series with the gain network, thus
eliminating the meter temperature coefficient error term.
Supply current in the standby position with the meter
undeflected is 300
A. At full-scale deflection this current
rises to 800
A. Carbon-zinc battery life should be in excess
of 1,000 hours.
Electrical Specifications
For Equipment Design, at V
SUPPLY
=
10V, T
A
= 25
o
C, Unless Otherwise Specified
PARAMETER
SYMBOL
TEST
CONDITIONS
CA3420
CA3420A
UNITS
MIN
TYP
MAX
MIN
TYP
MAX
Input Offset Voltage
|V
IO
|
-
5
10
-
2
5
mV
Input Offset Current (Note 4)
|I
IO
|
-
0.03
4
-
0.03
4
pA
Input Current (Note 4)
|I
I
|
-
0.05
5
-
0.05
5
pA
Large Signal Voltage Gain
A
OL
R
L
= 10k
10
100
-
20
100
-
kV/V
80
100
-
86
100
-
dB
Common Mode Rejection Ratio
CMRR
-
100
320
-
100
320
V/V
70
80
-
70
80
-
dB
Common Mode Input Voltage Range
V
lCR
+
8.5
9.3
-
9.0
9.3
-
V
V
lCR
-
-10
-10.3
-
-10
-10.3
-
V
Power Supply Rejection Ratio
PSRR
V
IO
/
V
-
32
320
-
32
320
V/V
70
90
-
70
90
-
dB
Max Output Voltage
V
OM
+
R
L
=
9.7
9.9
-
9.7
9.9
-
V
V
OM
-
-9.7
-9.85
-
-9.7
-9.85
-
V
Supply Current
I+
-
450
1000
-
450
1000
A
Device Dissipation
P
D
-
9
14
-
9
14
mW
Input Offset Voltage Temperature Drift
V
lO
/
T
-
4
-
-
4
-
V/
o
C
NOTE:
4. The maximum limit represents the levels obtainable on high speed automatic test equipment. Typical values are obtained under laboratory conditions.
3
CA3420
4
500-0-500
7
+1.5V
5
1
2
-1.5V
10pF
10G
10M
1M
BATTERY
RETURNS
10k
6
M
A
50pA
15pA
5pA
1.5pA
11k
1.5k
, 1%
1.5k
1k
430
, 1%
150
, 1%
68
1%
-
+
FIGURE 1. PICOAMMETER CIRCUIT
2
CA3420
4
500-0-500
7
+1.5V
5
1
3
-1.5V
10M
22M
BATTERY
RETURNS
10k
6
M
A
500mV
150mV
50mV
15mV
1.1k
1.5k
, 1%
1.5k
1k
430
, 1%
150
, 1%
68
1%
-
+
100pF
FIGURE 2. HIGH INPUT RESISTANCE VOLTMETER
CA3420, CA3420A
4
Typical Performance Curves
FIGURE 3. OUTPUT VOLTAGE SWING AND COMMON MODE
INPUT VOLTAGE RANGE vs SUPPLY VOLTAGE
FIGURE 4. OUTPUT VOLTAGE vs LOAD SOURCING CURRENT
FIGURE 5. OUTPUT VOLTAGE vs LOAD SINKING CURRENT
FIGURE 6. INPUT NOISE VOLTAGE vs FREQUENCY
FIGURE 7. OPEN LOOP GAIN AND PHASE SHIFT RESPONSE
V
O
-
R
L
= 100k
10
SUPPLY VOLTAGE (V)
15
T
A
= 25
o
C
-1.0
INPUT & OUTPUT V
O
L
T
A
GE EXCURSIONS FR
OM THE
V
O
+
V
ICR
-
V
ICR
+
5
1
0
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0
POSITIVE AND NEGA
TIVE SUPPL
Y V
O
L
T
A
GE (V)
V+ = 2V
V+ = 5V
V+ = 10V
V+ = 20V
10
1
0.1
0.01
LOAD (SOURCING) CURRENT (mA)
V- = 0V
T
A
= 25
o
C
1000
100
10
OUTPUT ST
A
GE TRANSIST
OR SA
TURA
TION
V
O
L
T
A
GE, Q
19
(mV)
V- = -2V
V- = -5V
V- = -10V
V- = -20V
10
1
0.1
0.01
LOAD (SINKING) CURRENT (mA)
10
100
1000
OUTPUT ST
A
GE TRANSIST
OR SA
TURA
TION
V
O
L
T
A
GE, Q
17
(mV)
V+ = 0V
T
A
= 25
o
C
V
S
=
10V
V
S
=
5V
V
S
=
1V
10
6
FREQUENCY (Hz)
10
5
10
4
10
3
10
2
10
1
1
10
100
1000
T
A
= 25
o
C
EQ
UIV
ALENT INPUT NOISE V
O
L
T
A
GE (nV/
Hz)
FREQUENCY (Hz)
10
6
10
5
10
4
10
2
10
1
1
10
3
V
S
=
5V
T
A
= 25
o
C
R
L
= 10k
C
L
= 0pF
0
20
40
60
80
100
-180
-135
-90
-45
0
OPEN LOOP V
O
L
T
A
GE GAIN (dB)
OPEN LOOP PHASE (DEGREES)
CA3420, CA3420A
5
CA3420, CA3420A
Dual-In-Line Plastic Packages (PDIP)
C
L
E
e
A
C
e
B
e
C
-B-
E1
INDEX
1 2 3
N/2
N
AREA
SEATING
BASE
PLANE
PLANE
-C-
D1
B1
B
e
D
D1
A
A2
L
A
1
-A-
0.010 (0.25)
C
A
M
B S
NOTES:
1. Controlling Dimensions: INCH. In case of conflict between
English and Metric dimensions, the inch dimensions control.
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
3. Symbols are defined in the "MO Series Symbol List" in Section
2.2 of Publication No. 95.
4. Dimensions A, A1 and L are measured with the package seated
in JEDEC seating plane gauge GS-3.
5. D, D1, and E1 dimensions do not include mold flash or protru-
sions. Mold flash or protrusions shall not exceed 0.010 inch
(0.25mm).
6. E and
are measured with the leads constrained to be per-
pendicular to datum
.
7. e
B
and e
C
are measured at the lead tips with the leads uncon-
strained. e
C
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).
e
A
-C-
E8.3
(JEDEC MS-001-BA ISSUE D)
8 LEAD DUAL-IN-LINE PLASTIC PACKAGE
SYMBOL
INCHES
MILLIMETERS
NOTES
MIN
MAX
MIN
MAX
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
0.355
0.400
9.01
10.16
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
-
e
A
0.300 BSC
7.62 BSC
6
e
B
-
0.430
-
10.92
7
L
0.115
0.150
2.93
3.81
4
N
8
8
9
Rev. 0 12/93
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