APPLICATIONS
GENERAL DESCRIPTION
ALD1123E/ALD1121E are monolithic quad/dual EPAD® (Electrically Program-
mable Analog Device) N-channel MOSFETs with electrically adjustable threshold
(turn-on) voltage. The ALD1123E/ALD1121E are precision matched and adjusted
(e-trimmed) at the factory resulting in quad/dual MOSFETs that are highly matched
in electrical characteristics. The ALD1123E has four (4) separate source pins. SN1,
SN2 share a common substrate pin V-1 which has to be connected to the most
negative voltage potential. Likewise, SN3, SN4 share a common substrate pin V-2
which has to be connected to the negative voltage potential for SN3, SN4. The
ALD1121E has two (2) separate source pins (SN1, SN2). Both SN1, SN2 share a
common substrate pin 4 which has to be connected to the most negative voltage
potential.
Using an ALD1123E/ALD1121E MOSFET array is simple and straight forward. The
MOSFETs function in electrical characteristics as n-channel MOSFETs except that
all the devices have exceptional matching to each other. For a given input voltage,
the threshold voltage of a MOSFET device determines its drain on-current, resulting
in an on-resistance characteristic that can be precisely preset and then controlled
by the input voltage very accurately. Since these devices are on the same monolithic
chip, they also exhibit excellent tempco matching characteristics.
These MOSFET devices have very low input currents, and as a result a very high
input impedance (>10 12 Ohm). The gate voltage from a control source can drive
many MOSFET inputs with practically no loading effects. Used in precision current
mirror or current multiplier applications, they can be used to provide a current source
over a 100 nA to 3 mA range, and with either a positive, negative or zero tempco.
Optional EPAD Threshold Voltage Trimming By User
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Precision PC-based electronic calibration
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Automated voltage trimming or setting
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Remote voltage or current adjustment of
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inaccessible nodes
PCMCIA based instrumentation trimming
Electrically adjusted resistive load
Temperature compensated current sources
and current mirrors
Electrically trimmed/calibrated current
sources
Permanent precision preset voltage level
shifter
Low temperature coefficient voltage and/or
current bias circuits
Multiple preset voltage bias circuits
Multiple channel resistor pull-up or pull-down
circuits
Microprocessor based process control systems
Portable data acquisition systems
Battery operated terminals and instruments
Remote telemetry systems
E-trim gain amplifiers
Low level signal conditioning
Sensor and transducer bias currents
Neural networks
BLOCK DIAGRAM
ALD1121E
P
N1
(1)
D
N1
(3)
D
N2
(7)
P
N2
(5)
G
N1
(2)
G
N2
(6)
The basic EPAD MOSFET device is a monotonically adjustable device which means
the device can normally be e-trimmed to increase in threshold voltage and to
decrease in drain-on current as a function of a given input bias voltage. Used as an
in-circuit element for trimming or setting a combination of voltage and/or current
characteristics, it can be e-trimmed remotely and automatically. Once e-trimmed,
the set voltage and current levels are stored indefinitely inside the device as a
nonvolatile stored charge, which is not affected during normal operation of the
device, even when power is turned off. A given EPAD device can be adjusted many
times to continually increase its threshold voltage. A pair of EPAD devices can also
be connected differentially such that one device is used to adjust a parameter in one
direction and the other device is used to adjust the same parameter in the other
direction.
The ALD1123E/ALD1121E can be e-trimmed with the ALD EPAD programmer to
obtain the desired voltage and current levels. Or they can be e-trimmed as an active
in-system element in a user system, via user designed interface circuitry. PN1, PN2,
etc., are pins required for optional e-trim of respective MOSFET devices. If unused,
these pins are to be connected to V- or ground. For more information, see
Application Note AN1108.
ALD1123E
M1
S
N1
(4)
V- (4)
BLOCK DIAGRAM
P
N1
(1)
G
N1
(2)
S
N1
(4)
V-
1
(4)
S
N2
(16)
S
N3
(12)
ALD1123E/ALD1121E
Advanced Linear Devices
~
~
M1
~
M2
S
N2
(8)
D
N1
(3)
D
N2
(15)
P
N2
(13)
P
N3
(9)
D
N3
(11)
D
N4
(7)
P
N4
(5)
G
N2
(14) G
N3
(10)
G
N4
(6)
M2
M3
M4
V-
2
(8)
S
N4
(8)
2
ALD [ ADVANCED LINEAR DEVICES ]
