PERFORMANCE CHARACTERISTICS OF EPAD®
PRECISION MATCHED PAIR MOSFET FAMILY
ALD2108xx/ALD2129xx/ALD2148xx/ALD2169xx high precision
The ALD2148xx/ALD2169xx (quad/dual) features Depletion Mode
EPAD MOSFETs, which are normally-on devices at zero applied
monolithic quad/dual N-Channel MOSFET arrays are enhanced
versions of theALD1108xx/ALD1109xx EPAD® MOSFET family, with
increased forward transconductance and output conductance, in-
tended for operation at very low power supply voltages. These de-
vices are also capable of sub-threshold operation with less than
1nA of operating supply currents and at the same time delivering
higher output drive currents (typ. > 50mA). They feature precision
gate voltage. The V
is set at a negative voltage level
GS(th)
< V ) at which the EPAD MOSFET turns off. Without a
(V- < V
GS
S
supply voltage and/or with V
= V- = 0.00V = Ground, the EPAD
GS
MOSFET device is already turned on and exhibits a defined and
controlled on-resistance R . An EPAD MOSFET may be
DS(ON)
turned off when a negative voltage is applied to V- pin and V
set
GS
. These Depletion Mode EPAD
Gate Offset Voltages, V
, defined as the difference in V
more negative than its V
OS
between MOSFET pairs M1 and M2 or M3 and M4.
GS(th)
GS(th)
MOSFETs are different from most other depletion mode MOSFETs
and JFETs in that they do not exhibit high gate leakage currents
and channel/junction leakage currents, while they stay controlled,
modulated and turned off at precise voltages. The same MOSFET
device equations as those for enhancement mode devices apply.
ALD's Electrically Programmable Analog Device (EPAD®) technol-
ogy provides the industry's only family of matched MOSFET tran-
sistors with a range of precision gate-threshold voltage values. All
members of this family are designed and actively programmed for
exceptional matching of device electrical and temperature charac-
KEY APPLICATION ENVIRONMENTS
teristics. Gate Threshold Voltage V
values range from -3.50V
GS(th)
Depletion Mode to +3.50V Enhancement Mode devices, including
EPAD MOSFETs are ideal for circuits requiring low V
and low
OS
standard products with V specified at -3.50V, -1.30V, -0.40V,
operating currents with tracked differential thermal responses. They
feature low input bias currents (less than 200pA max.), low input
capacitance and fast switching speed. These and other operating
characteristics offer unique solutions in one or more of the follow-
ing operating environments:
GS(th)
+0.00V, +0.20V, +0.40V, +0.80V, +1.40V, and +3.30V. ALD can
also provide any customer-desired V between -3.50V and
GS(th)
+3.50V on a special order basis. For all these devices ALD EPAD
technology enables excellent well-controlled gate threshold volt-
age, subthreshold voltage, and low leakage characteristics. With
well matched design and precision programming, units from differ-
ent production lots provide the user with exceptional matching and
uniformity characteristics. Built on the same monolithic IC chip, the
units also have excellent temperature tracking characteristics.
+
+
* Low supply voltage: 0.1V to 10V ( 0.05V to 5V)
+
+
* Ultra low supply voltage: < 10mV to 0.1V
* Nanopower operation: voltage x current = nW or µW
* Precision V
characteristics
OS
* Matching and tracking of multiple MOSFETs
* Matching across multiple packages
This ALD2108xx/ALD2129xx/ALD2148xx/ALD2169xx EPAD
MOSFETArray product family (EPAD MOSFET) is available in three
separate categories, each providing a distinctly different set of elec-
trical specifications and characteristics. The first category is the
ALD210800A/ALD210800/ALD212900A/ALD212900 Zero-Thresh-
old™ mode EPAD MOSFETs. The second is the ALD2108xx/
ALD2129xx enhancement mode EPAD MOSFETs. The third cat-
egory includes the ALD2148xx/ALD2169xx depletion mode EPAD
MOSFETs. (The suffix “xx” denotes threshold voltage in 0.1V steps,
for example, xx=08 denotes 0.80V). For each device, there is a
zero-tempco bias current and bias voltage point. When a design
utilizes such a feature, then the gate-threshold voltage is tempera-
ture stable, greatly simplifying certain designs where stability of
certain circuit parameters over a temperature range is desired.
ELECTRICAL CHARACTERISTICS
The turn-on and turn-off electrical characteristics of the EPAD
MOSFET products are shown in the I
vs. V
and
DS(ON)
DS(ON)
versus V
DS(ON)
I
vs. V graphs. Each graph shows I
DS(ON)
GS DS(ON)
characteristics as a function of V
GS
under different bias conditions, while I
in a different operating region
at a given gate input
DS(ON)
voltage is controlled and predictable. A series of four graphs titled
“Forward Transfer Characteristics”, with the 2nd and 3rd sub-titled
“expanded (subthreshold)” and “further expanded (subthreshold)”,
and the 4th sub-titled “low voltage”, illustrates the wide dynamic
operating range of these devices.
Classic MOSFET equations for an N-channel MOSFET also apply
to EPAD MOSFETs.
TheALD210800A/ALD210800 are quad Zero Threshold MOSFETs
in which the individual gate-threshold voltage of each MOSFET is
set at zero, V
= 0.00V at I
= 10µA @ V
= +0.1V
GS(th)
DS(ON)
DS(ON)
= 20µA for the dual ALD212900A/ALD212900). Zero
The drain current in the linear region (V
given by:
< V
GS
- V
) is
(I
DS(ON)
GS(th)
DS(ON)
Threshold MOSFETs operate in the enhancement region when op-
erated above threshold voltage (V > 0.00V and I > 10µA) and
GS
DS
subthreshold region when operated at or below threshold voltage
(V ≤ 0.00V and I < 10µA). These devices, along with other
I
= u . C
. W/L . [V
GS
- V
- V /2] . V
DS
DS(ON)
OX
GS(th)
DS(ON)
GS
low V
DS
members of the product family, enable ultra low supply
where:
u = Mobility
GS(th)
C
V
= Capacitance / unit area of Gate electrode
= Gate to Source Voltage
voltage analog or digital operation and nanopower circuit designs,
thereby reducing or eliminating the use of very high valued (expen-
sive) resistors in many cases.
OX
GS
V
= Gate Threshold (Turn-on)Voltage
= Drain to Source On Voltage
GS(th)
V
DS(ON)
W = Channel width
L = Channel length
The ALD2108xx/ALD2129xx (quad/dual) product family features
precision matched enhancement mode EPAD MOSFET devices,
which require a positive gate bias voltage V to turn on. Precision
GS
In this region of operation the I
value is proportional to the
value and the device can be used as a gate-voltage con-
V
values at +3.30V, +1.40V, +0.80V, +0.40V and +0.20V are
DS(ON)
GS(th)
offered. No conductive channel exists between the source and drain
at zero applied gate voltage (V = 0.00V) for +3.30V, +1.40V and
V
DS(ON)
trolled resistor.
GS
+0.80V versions. The +0.40V and the +0.20V versions have a sub-
threshold current at about 1nA and 100nA for the ALD2108xx (2nA
and 200nA for the ALD2129xx) respectively at zero applied gate
For higher values of V
saturation current I
where V
≥ V
DS(ON) GS
- V
, the
GS(th)
DS(ON)
is now given by (approx.):
DS(ON)
voltage. They are also capable of delivering lower R
and
higher output currents greater than 68mA (see specifications).
DS(ON)
2
I
= u . C
OX
. W/L . [V
- V ]
GS(th)
DS(ON)
GS
ALD212908A/ALD212908
Advanced Linear Devices
3 of 12
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