GENERAL DESCRIPTION

The ALD212908A/ALD212908 precision enhancement mode N-Channel EPAD®

MOSFET array is precision matched at the factory using ALD’s proven EPAD®

CMOS technology. These quad monolithic devices are enhanced additions to

the ALD212908A/ALD212908 EPAD® MOSFET Family, with increased forward

transconductance and output conductance, particularly at very low supply voltages.

Intended for low voltage, low power small signal applications, the ALD212908A/

ALD212908 features precision threshold voltage, which enables circuit designs

with input/output signals referenced to enhanced operating voltage ranges. With

these devices, a circuit with multiple cascading stages can be built to operate at

extremely low supply/bias voltage levels. For example, a nanopower input amplifier

stage operating at less than 1.0V supply voltage has been successfully

built with these devices.

ALD212908A EPAD MOSFETs feature exceptional matched pair electrical characteristics

of Gate Threshold Voltage VGS(th) set precisely at +0.80V +0.01V,

IDS = +20μA @ VDS = 0.1V, with a typical offset voltage of only +0.001V (1mV).

Built on a single monolithic chip, they also exhibit excellent temperature tracking

characteristics. These precision devices are versatile as design components

for a broad range of analog small signal applications such as basic building

blocks for current mirrors, matching circuits, current sources, differential amplifier

input stages, transmission gates, and multiplexers. They also excel in limited

operating voltage applications, such as very low level voltage-clamps and

nano-power normally-on circuits.

In addition to precision matched-pair electrical characteristics, each individual

EPAD MOSFET also exhibits well controlled manufacturing characteristics, enabling

the user to depend on tight design limits from different production batches.

These devices are built for minimum offset voltage and differential thermal response,

and they can be used for switching and amplifying applications in +0.1V

to +10V (+0.05V to +5V) powered systems where low input bias current, low

input capacitance, and fast switching speed are desired. At VGS > +0.80V, the

device exhibits enhancement mode characteristics whereas at VGS < +0.80V

the device operates in the subthreshold voltage region and exhibits conventional

sub threshold characteristics, with well controlled turn-off and sub-threshold

levels that operate the same as standard enhancement mode MOSFETs.

The ALD212908A/ALD212908 features high input impedance (2.5 x 1010Ω) and

high DC current gain (>108). A sample calculation of the DC current gain at a

drain output current of 30mA and input current of 300pA at 25°C is 30mA/300pA

= 100,000,000, which translates into a dynamic operating current range of about

eight orders of magnitude. 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.

Generally it is recommended that the V+ pin be connected to the most positive

voltage and the V- and IC (internally-connected) pins to the most negative voltage

in the system. All other pins must have voltages within these voltage limits

at all times. Standard ESD protection facilities and handling procedures for static

sensitive devices are highly recommended when using these devices.

FEATURES & BENEFITS

• Precision VGS(th) = +0.80V +0.010V

• VOS (VGS(th) match) to 2mV/10mV max.

• Sub-threshold voltage (nano-power) operation

• < 800mV min. operating voltage

• < 1nA min. operating current

• < 1nW min. operating power

• > 100,000,000:1 operating current ranges

• High transconductance and output conductance

• Low RDS(ON) of 14Ω

• Output current > 50mA

• Matched and tracked tempco

• Tight lot-to-lot parametric control

• Positive, zero, and negative VGS(th) tempco

• Low input capacitance and leakage currents

APPLICATIONS

• Low overhead current mirrors and current sources

• Zero Power Normally-On circuits

• Energy harvesting circuits

• Very low voltage analog and digital circuits

• Zero power fail-safe circuits

• Backup battery circuits & power failure detector

• Extremely low level voltage-clamps

• Extremely low level zero-crossing detector

• Matched source followers and buffers

• Precision current mirrors and current sources

• Matched capacitive probes and sensor interfaces

• Charge detectors and charge integrators

• High gain differential amplifier input stage

• Matched peak-detectors and level-shifters

• Multiple Channel Sample-and-Hold switches

• Precision Current multipliers

• Discrete matched analog switches/multiplexers

• Nanopower discrete voltage comparators