JAN-03 Datasheet, PDF (2/5 Pages) Vishay Siliconix – Basic Definitions

Vishay Semiconductors
VISHAY
Polarity conventions for diodes
Here, the direction of arrows is selected in such a way
that the numerical values of currents and voltages are
positive both for forward (F or f) and reverse (R or r)
directions.
A
I_F
K
V_F
A
I_R
K
V_R
Figure 3.
Arrangement of Symbols
Letter symbols for current, voltage and power
(according to DIN 41 785, sheet 1)
To represent current, voltage and power, a system of
basic letter symbols is used. Capital letters are used
for the representation of peak, mean, DC or root-
mean-square values. Lower case letters are used for
the representation of instantaneous values which
vary with time.
Capital letters are used as subscripts to represent
continuous or total values, while lower case letters are
used to represent varying values.
The following table summarizes the rules given above
.
Basic letter
Upper-case
Upper-case
Instantaneous values which
vary with time
Maximum (peak) average
(mean) continuous (DC) or
root-mean-square (RMS)
values
Subscript(s)
Upper-case
Upper-case
Varying component alone, i.e.,
instantaneous,
root-mean-square, maximum
or average values
Continuous (without signal) or
total (instantaneous, average or
maximum) values
Letter symbols for impedance, admittances, two-
port parameters etc.
For impedance, admittance, two-port parameters,
etc. capital letters are used for the representation of
external circuits of which the device is only a part.
Lower case letters are used for the representation of
electrical parameters inherent in the device.
CAPITAL letters are used as subscripts for the desig-
nation of static (DC) values, while lower case letters
are used for the designation of small-signal values.
If more than one subscript is used (h_FE, h_fe), the letter
symbols are either all capital or all lower case.
If the subscript has numeric (single, double, etc.) as
well as letter symbol(s) (such as h_21E or h_21e'), the dif-
ferentiation between static and small-signal value is
made only by a subscript letter symbol.
Other quantities (values) which deviate from the
above rules are given in the list of letter symbols.
The following table summarizes the rules given above
.
Basic letter
Upper-case
Upper-case
Electrical parameters inherent
in the semiconductor devices
except inductances and
capacitances
Electrical parameters of
external circuits and of circuits
in which the semiconductor
device forms only a part; all
inductances and capacitances
Upper-case
Small-signal values
Subscript(s)
Upper-case
Static (dc) values
Examples:
G_P Power gain
Z_S Source impedance
f_T Transition frequency
I_F Forward current
Example for the use of symbols
according to 41785 and IEC 148
V_F
V_FSM
V_FRM
V_FWM
0
V_RWM
V_RRM
V_RSM
V_R
t
93 7796
Figure 4.
V_F Forward voltage
V_R Reverse voltage
V_FSM Surge forward voltage (non-repetitive)
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Document Number 84067
Rev. 7, 07-Jan-03