DEFINITION OF TERMS
Bias Voltage (V
BIAS
)
Bias Voltage of an EPAD is the voltage across Gate and Source terminals with Gate and Drain connected at a specified
Drain to Source Current, I
DS.
When I
DS
= 1µA, Bias Voltage is identical to Threshold Voltage. Input Bias Voltage of an
EPAD is the voltage across Gate and Source terminals, V
GS
. Output Bias Voltage of an EPAD is the voltage across Drain
and Source terminals V
DS
at a specified Drain to Source Current, I
DS
.
Change in Threshold Voltage Per Programming Pulse (
∆
V
t
/ N)
This is the voltage change in Threshold Voltage while the EPAD is being programmed with an electrical voltage pulse.
This voltage change can be very small as it varies as an exponential function of Vt. Typical initial values range from
0.1 mV/step to 1.0mV/step when Vt = 1 Volt and decreases to 10µV/step or lower at higher Vt values.
Delta Threshold Voltage (
∆
Vt)
Delta Threshold Voltage is a change in the threshold voltage of the same EPAD device after programming.
Differential Threshold Voltage (DVt)
Differential Threshold Voltage is the difference of Vt between the two EPAD devices, each electrically programmed to a
different Vt value. This is also a fixed relative voltage that tracks with temperature, with tempco value of TC DVt for 1 volt
relative Vt between two EPADs.
EPAD™
Electrically Programmable Analog Device is an Integrated Circuit that utilizes CMOS FET with electrically programmable
Threshold Voltage. Once programmed, the set Threshold Voltage is retained indefinitely, even when power is off.
Initial Threshold Voltage (V
t i
)
The initial Vt of a device before being electrically programmed to a new Vt value.
Initial Zero Tempco Voltage (V
ZTCi
)
Initial Drain Voltage at which the Temperature Coefficient of the Drain-Gate connected Voltage, relative to the Source
Voltage, is at zero, when the initial Vt is at 1.000 volt.
Long Term Drift (
∆
Vt /
∆
t)
Long Term Drift is the nominal change in threshold voltage of an EPAD for a time period of 1,000 hours.
Long Term Drift Match (
∆
Vt /
∆
t)
Long Term Drift Match is the nominal match in long term drift between two EPADs, for a time period of 1,000 hours.
Monotonic Adjustment of Vt
Vt Adjustment can be changed in one direction only.
Offset Voltage (V
OS
)
Offset Voltage is the small difference in Vt between two EPAD devices when the two devices have the same initial
electrically programmed Vt values.
Programming Voltage (Vp)
The voltage at which programming of the threshold voltage of the EPAD occurs. This voltage, the control of timing of this
voltage and the impedance of the voltage source is critical to the way the EPAD is programmed and its subsequent device
performance. The user is advised to use an ALD EPAD programmer which has been specifically designed and developed
for this task.
Relaxation Time Constant (t
RLX
)
Relaxation Time Constant is the time constant associated with the Relaxation Voltage drop after an EPAD has
been programmed.
ALD1108E/ALD1110E
Advanced Linear Devices
9
ALD [ ADVANCED LINEAR DEVICES ]
